NATIONAL NEWS (CNN) — The Obama administration will spend this week trying to persuade lawmakers at home and allies abroad that an attack on Syria is the appropriate response to the alleged use of poison gas by President Bashar al-Assad's regime.
The White House push comes after al-Assad once again raised the specter of an all-out regional war if the United States strikes.
Syria's allies Russia and China, meanwhile, remain steadfastly opposed to military action, unconvinced by evidence that the United States and France say shows al-Assad's forces used chemical weapons in an August 21 attack around Damascus.
Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff; Secretary of State John Kerry; and Defense Secretary Chuck Hagel are all scheduled to appear before the Senate Foreign Relations Committee Tuesday to press the case for action against Syria, a senior State Department official said.
Kerry will argue that a failure to act "unravels the deterrent impact of the international norm against chemical weapons use," said the official, who spoke on condition of anonymity.
A senior Pentagon official told CNN Dempsey will focus in his testimony on answering questions from the members about the use of military force, rather than making an overt case for military action. This would be in line with Dempsey's views that the military will be ready to do whatever the president orders.
It will mainly be Hagel who makes the case that the use of force is warranted, a second senior defense official said. Both declined to be identified because they were speaking in advance of the hearing.
The president was to meet Tuesday morning with House Speaker John Boehner and Minority Leader Nancy Pelosi, congressional aides said, and he has already planned talks with the leaders of the key national security committees in the House and Senate.
Administration officials will also be conducting classified briefings on Syria for Congress nearly every day this week.
Israeli missile test
Amid heightened tension in the region, Israel carried out a missile test Tuesday morning in the Mediterranean -- a launch detected by a Russian early warning system before it was confirmed by Israeli authorities.
Israel's Ministry of Defense said it and the U.S. Missile Defense Agency "completed a successful flight test (of the) new version of the Sparrow target missile."
The trial was carried out from an Israeli test range over the Mediterranean Sea, it said. The Arrow defense system successfully detected and tracked the system, it added.
Earlier, a Ministry of Defense Facebook post said an Anchor target missile was the type tested.
A U.S. official told CNN it was "an expected Israeli system test" in the eastern Mediterranean Sea. The official said it was up to the Israelis to explain exactly what they were testing.
"No ballistic missile launch has been detected. None at our ships, and none by our ships. There have been no offensive or defensive missile launches by the U.S. military," a U.S. military official told CNN. The official was adamant that "this did not involve U.S. forces."
Five U.S. warships were in the Mediterranean Sea last week.
Ben Goodlad, a senior defense analyst at IHS Jane's, said that a target missile "has similar ballistic characteristics as a missile. However, it does not feature a warhead and is intended to merely simulate a launch in order to test detection, tracking and interception capabilities."
This is likely why there was no reported missile strike, he said. Any missiles fired against Syria from vessels in the Mediterranean would be Tomahawk cruise missiles, he said, "which follow a far flatter trajectory than ballistic missiles and would not be mistaken as such by early warning radar."
Russia's Defense Ministry said it detected the launch of two "ballistic objects" from the Mediterranean Sea toward the eastern Mediterranean coast at 2:16 a.m. ET, Russian news agency RIA-Novosti reported. Defense Minister Sergey Shoigu informed President Vladimir Putin of the development, it added.
Bill Neeley, international editor for CNN affiliate ITN, tweeted from Damascus that there have been "no major explosions in #Damascus area that might have been from missiles fired from Med. Several blasts 2 hrs ago from army to rebel areas."
'A lot of distrust'
In the United States, the Obama administration is expected to increase its lobbying efforts as lawmakers return to Capitol Hill for briefings.
A leading member of one of the key U.S. committees, House Armed Services Committee Chairman Buck McKeon, said the administration will have to overcome "a lot of distrust among the American people" about the intelligence that it says shows Syria's government used chemical weapons.
"There will be a real questioning as to the veracity of the evidence and if this really happened or not," McKeon, R-California, said in an interview with CNN's Barbara Starr. "It will be necessary to explain and prove to the American people, and I think the only person who can really do that is the president of the United States."
The United States and several of its leading allies accuse al-Assad's forces of resorting to poison gas attacks against rebel forces and civilians, including an August 21 attack near Damascus the Obama administration says killed more than 1,400 people.
Obama said Saturday that the use of chemical weapons is "a challenge to the world" that threatens U.S. allies in the region -- but he said he would seek the authorization of Congress before unleashing American force.
No vote on military action is expected until after lawmakers reconvene from recess on September 9.
More support for the opposition
U.S. plans for strikes against Syria may be coupled with increased support for rebel forces in that country's civil war, two leading Republican senators said after meeting with the president on Monday.
Obama huddled in the Oval Office with McCain and Sen. Lindsey Graham, both members of the Senate Armed Services Committee, the White House said. After the meeting, McCain and Graham said the United States needs to help the rebels reverse battlefield gains by troops loyal to al-Assad.
"We still have significant concerns, but we believe there is in formulation a strategy to upgrade the capabilities of the Free Syrian Army and to degrade the capabilities of Bashar al-Assad," said McCain, the ranking Republican on the armed services committee.
McCain, who has called for U.S. intervention in Syria since early 2012, criticized Obama's decision to seek a vote before striking. But he said it would be "catastrophic" for Congress to reject the president's call to authorize military force.
"It would undermine the credibility of the United States of America and the president of the United States," McCain said. "None of us want that."
In an interview with CNN Tuesday, McCain added that he wants Congress to vote for a resolution that is "meaningful, impactful and can shift the balance of power on the ground in Syria."
McCain, a former Republican presidential candidate, said delays to U.S. military strikes are giving the Syrian military time to move its assets into safety and risks putting more civilians in danger.
Graham told CNN that Obama must do more to convince the American people of the need for action on Syria. The senator believes Iran will be emboldened to continue its pursuit of nuclear weapons if no international action is taken against Syria, and the region will be further destabilized.
"If we get Syria right, maybe we can avoid a war between Israel and Iran which we would surely get (dragged) into," he said. "If we fail to stand up for the right thing and send the right message, the whole region will go up in flames."
Lawmaker's 'big question'
The threat of a regional war is an angle that the Syrian president continues to flag.
"The Middle East is a powder keg, and the fire is approaching today," he told French newspaper Le Figaro in an interview Monday.
"One must not speak only of the Syrian response, but rather what could be produced after the first strike," he said. "Because nobody can know what will happen."
Neither Washington nor Paris has "a single proof" that the Syrian government was behind the alleged chemical weapons attack against civilians on August 21, he said.
Obama would have gone back to the U.N. Security Council if he were a strong leader, Assad said, but instead he has given in to pressure to act from within the United States.
Syria has repeatedly denied being behind the August 21 attack and accuses rebel fighters of using chemical weapons on government troops.
U.N. weapons inspectors left Syria Saturday with evidence that will determine whether poison gas was used in that attack and tests on those samples are being conducted "as fast as it is possible to do within the scientific constraints," said Martin Nesirky, spokesman for Secretary-General Ban Ki-moon.
The United Nations has said more than 100,000 people -- including many civilians -- have been killed in Syria since a popular uprising spiraled into a civil war in 2011. Syrian opposition activists reported another 107 dead on Monday, mostly in Damascus and its suburbs.
Numbers released by the United Nations Tuesday point to the staggering impact the war has had on the nation.
The number of Syrians who have fled their war-ravaged country has risen above 2 million, the U.N. refugee agency reported, an increase of nearly 1.8 million people over the past 12 months.
CNN's Matt Smith, Elise Labott, Alla Eshchenko, Michael Schwartz, Evan Perez, Barbara Starr, Dana Bash, David McKenzie, Ashley Killough, Sarah Chiplin, Khushbu Shah, Mohammed Tawfeeq, Sandrine Amiel and Niki Cook contributed to this report