Amid tensions over Jewish settlement activities, U.S. President Barrack Obama met with Israeli Defense Minister Ehud Barak on Monday at the White House, reaffirming U.S. "unshakeable" commitment to Israel's security.

White House spokesman Robert Gibbs told reporters that during the meeting, which was joined by National Security Adviser James Jones, President Obama also reiterated his determination to achieve a comprehensive peace in the Middle East.

The spokesman gave no more details on the meeting. Reports here said the two sides also discussed immediate challenges to Israel's security and the regional stability, including Iran's nuclear threat and the alleged Syria's missiles supply for the Hezbollah guerrillas.

The Obama administration was "encouraged by the productive nature" of the recent talks between envoy George Mitchell and leaders of Israel and the Palestinians, said Gibbs, referring to the latest U.S. efforts to improve the atmosphere for peace and for proceeding with proximity talks between the Israeli government and the Palestinian National Authority (PNA).

Mitchell is expected to be back to Israel and the West Bank in the coming days. The United States has asked both sides to take steps to rebuild trust and to create momentum necessary for advancing the peace talks, according to State Department spokesman Philip Crowley, "We're not going to go into details about what we've asked them to do, but obviously this is an important issue in the atmosphere to see the advancement of peace."

Washington has been very angry at the Netanyahu-led government's uncompromising stance on peace process with the Palestinians, considering Israel's settlement activities in East Jerusalem as an unacceptable pullback to the U.S. efforts for peace guided by the two-state solution.

The Obama administration has been exerting efforts to pressure on the Israeli government and the PNA to resume the talks, so that the two sides could reach a permanent peace agreement that leads to the establishment of an independent Palestinian state within two years.

The talks were stalled in December 2008 when Israel launched a massive military campaign against the Islamic Hamas movement in the Gaza Strip.

PNA Chairman Mahmoud Abbas insists that the talks shall not resume until the Israeli government totally freezes the Jewish settlement construction in the West Bank, while the Israeli side vows to ensure the "natural growth" of the Jewish settlements.

At least 450,000 Israelis live in more than 100 settlements in the West Bank, including East Jerusalem.

After Israel's announcement to build 1,600 homes in East Jerusalem early in March, the PNA decided to suspend the proximity talks with Israel, which was brokered by U.S. envoy Mitchell following months-long tireless shuttle mediations between Israel and the Palestinians.