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 presented by the United States and France that they say show al-Assad's forces used chemical weapons in an August 21 attack around Damascus.
Amid heightened tensions 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.
"The Israeli Ministry of Defense and the U.S. Missile Defense Agency have completed successfully a launch, and observation from radar of the 'Anchor' target missile," said a spokeswoman at Israel's Ministry of Defense.
The ministry's Facebook page said the test was "carried out in the Mediterranean Sea, and from a test site in an Israeli Air Force base in a central part of the country. In the test they checked out the improved ability of the new target missile 'Anchor.' And they checked the defense systems against missiles of the 'Arrow' system, including radar and system controls."
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 "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 am 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."
In the United States, the Obama administration is expected to increase its lobbying efforts as lawmakers return to Capitol Hill for briefings.
Gen. Martin Dempsey, chairman of the Joint Chiefs of Staf; 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.
And administration officials will be conducting classified briefings on Syria for Congress nearly every day this week. The president will 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.
'A lot of distrust'
A leading member of one of those 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.
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 Sens. John McCain and 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."
No vote on military action is expected until after lawmakers reconvene from recess on September 9.
Lawmaker's 'big question'
Rep. Janice Hahn, D-California, told CNN that many of those who have listened to administration briefings have questions that have not been resolved.
She said her "big question" was whether there was a way to hold Syria's government accountable for violating the post-World War I taboo against chemical weapons "besides this seemingly unclear military strike that could lead to much more conflict in the Middle East."
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."
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.
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