The annual meeting of heads of state, which kicks off on Wednesday, comes after US Secretary of State Condoleezza Rice appealed to Arab governments to "begin reaching out to Israel" by building on the peace blueprint first adopted at a summit in Beirut in 2002.

Arab foreign ministers agreed to revive the plan in preparatory talks on Monday. The blueprint offers Israel full normalisation of relations if it withdraws from all lands it occupied in 1967, and permits the creation of a Palestinian state and the return of Palestinian refugees.

Saudi Arabia, a US ally and author of the blueprint, lobbied fellow Arab states to endorse the plan's revival, leaning particularly on the Palestinian Islamist movement Hamas, which now leads a government of national unity with the Fatah party of president Mahmud Abbas.

Hamas Prime Minister Ismail Haniya and Abbas flew into Riyadh aboard the same plane in a show of unity.

Exiled Hamas leader Khaled Meshaal also reportedly assured Saudi Arabia that the group, which does not recognise Israel, will back whatever consensus the Arab summit reaches on the peace plan.

Palestinian foreign minister Ziad Abu Amr, an independent in the new unity cabinet who is seen as an acceptable interlocutor by the West, told AFP that the international community should "isolate Israel" if it spurns the Arab peace offer.

Earlier Israeli and Palestinian leaders have agreed to meet every two weeks to discuss day-to-day issues, but also a "political horizon," Secretary of State Condoleezza Rice announced Tuesday after shuttling between the two sides for three days.

Rice also said her envoy will try to set benchmarks for implementing a ceasefire, including the halting of rocket fire from Gaza, and for improving the flow of Palestinian travellers and goods through Israeli crossings.