Mr Gates's talks in Israel were expected to centre on Iran's disputed nuclear efforts, while MrMitchell will focus on the US's drive to reach a comprehensive peace between Israel, the Palestinians, Syria and Lebanon.

Amid continuing discord over settlements, one of the main stumbling blocks in the stalled peace process, a report in the Haaretz newspaper revealed that the number of settlers in the occupied West Bank now exceeded 300,000.

Israel's refusal to heed US demands to stop all settlement activity on occupied Palestinian land has caused tensions between the two staunch allies to rise to a level not seen in years.

The US Defence Secretary met his Israeli counterpart, Ehud Barak, and was to have a working lunch with Prime Minister Benjamin Netanyahu on his one-day visit.

Mr Mitchell, meanwhile, was meeting Egyptian President Hosni Mubarak in Cairo before heading to the West Bank for talks with Palestinian President Mahmoud Abbas. He will meet Mr Netanyahu today.

Egypt is a key regional player and has been mediating unity talks between rival Palestinian groups Fatah and Hamas, and between Israel and Hamas for a prisoner swap to try to secure the release of an Israeli soldier held in Gaza.

''The US is committed to a comprehensive peace in the Middle East and that includes Israel and Palestine, Israel and Syria, Israel and Lebanon and normal relations with all countries in the region,'' MrMitchell was quoted as saying after meeting Mr Mubarak on Sunday.

Mr Mitchell began his latest regional tour in Damascus, his second visit since last month to a country that US President Barack Obama has sought to re-engage as part of a changed approach to the region from his predecessor, George W. Bush.

In the Syrian capital, the former US senator said he had a ''very candid and positive conversation'' with President Bashar al-Assad.