By James Robbins Diplomatic correspondent, BBC News

The Quartet tried to balance the pressure on both sides

Momentum. That was the word on everyone's lips.

The quartet of Middle East mediators - the US, Russia, the EU and the UN - are seizing on the possibility that for the first time since the collapse of former US President Bill Clinton's Camp David talks seven years ago there could, just could, be an opening towards peace.

The quartet, and their special envoy, former British Prime Minister Tony Blair, remained, deliberately, very cautious indeed but there is at least a sense of a path towards peace that does not look utterly blocked.

Warnings

Tony Blair said he wanted to put hope back in the Middle East peace process in an "ambitious but achievable" effort to help build a Palestinian state.

We all have to take risks... [or] peace will slip further into the future... perhaps by up to five years Javier Solana, EU foreign policy chief

Mr Blair stressed the need for Palestinians to create the institutions of "a serious well-functioning state" - good government, security forces and a legal and judicial system that would give hope "to ordinary people on both sides that things are going to improve".

So Russia, the EU and the UN offered strong support for US Secretary of State Condoleezza Rice and for the international meeting called for November by President George W Bush.

Ms Rice stressed that all the key issues could be discussed and that Arab states, including Syria, would be among those invited.

But she also called on Syria to renounce the use of violence and to accept that the purpose of an international meeting was to support Israel and the Palestinians in seeking a "two state solution".

As usual from the quartet, considerable effort went into balancing pressures on, and criticism of, both the Israeli and Palestinian sides.

So warnings to Israel: "The quartet expressed concern over conditions in Gaza. It agreed on the importance of continued emergency and humanitarian assistance without obstruction."

And a warning to the Palestinians: "The quartet further noted its grave concern over the continued rocket fire from Gaza into Israel."

Work together

Just before the meeting, the EU foreign policy chief, Javier Solana, one of the quartet members, told me that the next few months represented "a rare opportunity".

"We all have to take risks," he said, while cautioning against too much optimism.

Mr Solana warned that if this chance was missed, things would not just stay as they were.

"Peace will slip further into the future... perhaps by up to five years," he said.