By the BBC's Ed Butler

The Middle East peace talks underway in the United States are being seen as the last big piece in a diplomatic jigsaw designed to solve half a century of conflict.

Israel and Syria have long been at opposing ends of the Middle Eastern divide, and have now come together in Shepherdstown, West Virginia.

According to Israeli Prime Minister Ehud Barak the price of peace may be painful, but it is necessary.

He states Israel's security will be strengthened by ending the conflict with Syria, by demilitarising the Golan Heights, redeploying the Syrian army away from Israel's borders, securing their water sources, and ending "the tragedy in Lebanon".

The move would also "make a qualitative leap" in the strategic co-operation with the United States, and bring North African states and the Arabian peninsula into the process he says.

Despite such benefits, Mr Barak insists that he will not be sacrificing too much to win them.

Syrian concessions

He is going to require some major concessions from Syria if Israel is to finally relinquish what it regards as the main prize, the Golan Heights.

This mountainous stretch of land was seized by Israel during the six-day war of 1967.

It has become home to some 17,000 Israeli settlers and offers Israel a natural strategic buffer to Syria.

The BBC's State Department correspondent Richard Lister believes it remains to be seen whether Israel is really ready to give it up:

"I think it's no secret that the Israelis are talking because they are prepared to withdraw from the Golan, but the devil is in the details and that is the stage we are at".

Those details are to what border the troops withdraw from: the 1967 border, or the original Palestine border with Syria of 1923?

Precious water

Another question is whether part of the border will be made available to the Israelis for the collection of water.

Water is a prized asset in this region, especially to Syria, according to the Syrian writer and commentator Rana Kabbani.

"Syria is extremely worried about water because it has had a major drought in the last few years" he said.

"Syria's economy, unlike Israel's, is still agrarian-based, and with its loaded history of conflict with Turkey over water. I think it won't reach an agreement without a guarantee of a decent supply".

That will mean Syria demanding the handover of the source of the Baniyas River, which lies within the Golan territory.

In return Israel wants concrete security safeguards - possibly in the form of semi-militarised advance warning posts inside the Golan and elsewhere.

For Israel, normalised relations with Syria would grant it one clear benefit - the freedom to withdraw with impunity from the 'buffer' territory in southern Lebanon.

This border area, patrolled by Israeli troops, has cost it billions of dollars and many lives in the approximately 18 years Israel has been there.

Israel would probably be relieved to pull out now that the Syrian-backed Lebanese Hezbollah guerrilla group is no longer a threat.

But Syria must first prove its serious desire for peace, according to Israeli Government spokesman Moshe Fogel:

"The Syrian Government must convince the Israeli electorate that it is in our interest to end the conflict - we can only be convinced if the Syrians completely and totally change their attitudes."

Historic time

President Clinton and his Secretary of State Madeleine Albright worked hard to push both camps towards a deal at last month's preliminary talks.

In the past their influence has been central in keeping the peace process alive.

Mrs Albright does not expect these talks to conclude quickly however. "I'm sure there will be more than one round in this," she said.

"We are all aware how problematic the issues are, but obviously we are all very much seized with the idea that this is an historic time."