Israel has carried out a joint missile test with the US in the Mediterranean, amid heightened tension over possible Western military strikes on Syria.
The test came as the US Congress prepared for its first public hearing on a possible military response to alleged chemical weapons use by Syria.
Earlier, the UN confirmed that more than two million Syrians were now refugees from the 30-month conflict.
More Syrians were now displaced than any other nationality, it said.
A senior Israeli defense official confirmed to the BBC that a missile had been fired on Tuesday to test its defense systems.
The defense ministry said Israel's Arrow missile defense system had successfully detected and tracked a Sparrow medium-range guided missile fired as part of the test.
The BBC's Richard Galpin in Jerusalem said tests like this are usually planned long in advance.
But he said it is still a sign that Israel is taking very seriously the possibility that any US air strikes could lead to retaliatory attacks on Israel — either by Syria itself or by its ally, the Shia militia Hezbollah in Lebanon.
The US Congress is set to begin its hearings on the case for intervention, with President Barack Obama seeking to persuade skeptical politicians and the American people of the need for a military response to the suspected chemical weapons attack on the outskirts of Damascus on 21 August.
The US has put the death toll from the attack at 1,429, including 426 children, though other countries and organizations have given lower figures.
Secretary of State John Kerry, Defence Secretary Chuck Hagel and the top US military officer, Gen Martin Dempsey, are to appear before the Senate Committee on Foreign Relations.
There will also be a classified briefing for all members of Congress.
President Obama is also meeting the leaders of a number of House and Senate committees, including armed services, foreign relations and intelligence.
He said that Syrian President Bashar al-Assad had to be held accountable for the chemical attack and that he was confident Congress would back military action.
Obama said he was proposing limited military action that would degrade President Assad's capacity to use chemical weapons "now and in the future," while the US would also conduct a broader strategy of upgrading the capabilities of the opposition.
A vote in Congress is expected next week.
Read the full story and updates at BBC News.