Gordon Brown and Tony Blair teamed up yesterday to try to salvage a planned Middle East peace conference in America by clinching Saudi Arabia’s attendance.

According to British officials, first the Prime Minister and then his predecessor met King Abdullah of Saudi Arabia yesterday. It was made clear at the meetings that the country’s participation was crucial for what is being billed as the best chance for peace in the region for seven years.

“Saudi Arabia’s participation is essential,” one British source told The Times. “A meeting without the Saudis would be dead in the water.”

The conference is supposed to take place this month in Annapolis, Maryland, but so far no invitations have been sent out and there are growing fears that the event may be postponed indefinitely because of a lack of faith among Arab leaders in the commitment of the Bush Administration.

That is why the Brown-Blair diplomatic intervention is so important. Mr Blair, who coordinates the efforts of the Quartet on the Middle East, has been travelling widely in the region and met President Bush at the White House last month to discuss peace efforts. Mr Brown, a relative novice to Middle East diplomacy, met Ehud Olmert, the Israeli Prime Minister, in Downing Street last week, followed by King Abdullah yesterday.

Condoleezza Rice, the US Secretary of State, leaves for the region tomorrow for her second trip in as many weeks to try to pin down the agenda and the participants.

According to Downing Street, Mr Brown told King Abdullah that the Saudis must play a leadership role at Annapolis, but getting them on board is proving difficult. King Abdullah is known to feel very strongly about the plight of the Palestinians and the need for a settlement to the Arab-Israel conflict. He is the author of the current Arab peace initiative, whereby the Arab world would recognise Israel’s existence once Israel and the Palestinians agree to a two-state solution.

The Saudi ruler is reluctant, however, to commit a Saudi delegation to sitting down with Israelis, for the first time in history, unless the Israelis offer serious concessions to the Palestinians first. The Saudis want them to improve the situation in the West Bank and Gaza by releasing prisoners, dismantling checkpoints and halting the construction of Jewish settlements on Arab land. They also want a document to set out the aims of the conference and a timetable. The Annapolis conference seeks to resolve the thorniest issues in the conflict, namely the status of Jerusalem, claimed by both sides as their capital, the fate of millions of Palestinian refugees and the demarcation of a future Palestinian state.

Israel wants a far more vague document that simply outlines the aims of the conference. It also strongly resists any wording that could be interpreted as a deadline for withdrawing its forces from the West Bank.

The process is clouded by the relative weakness of the key participants. President Bush has only a year before US presidential elections. Mr Olmert remains weak and unpopular. Mahmoud Abbas, the Palestinian leader, does not even control the Gaza Strip, which is now in the hands of Hamas.

America can probably count on the attendance of its moderate allies in the region, such as Egypt and Jordan, as well as Israel and the Palestinians but hardliners such as Syria are doubtful.