Arafat flew into Andrews Air Force Base outside Washington after a stopover in London for talks with British Prime Minister Tony Blair. Arafat made no public comment on his arrival for the summit, which was scheduled to begin on Thursday with a White House meeting between the Palestinian leader, President Bill Clinton, and Israeli Prime Minister Benjamin Netanyahu.

Arafat and Netanyahu are then due to launch formal negotiations at the Wye River Conference Center, a luxurious retreat on the Chesapeake Bay in eastern Maryland. The talks are scheduled to last at least until Sunday and could continue into next week, US officials said.

The goal of the negotiations is to seal a new interim peace agreement involving further Israeli withdrawals from the West Bank and tougher Palestinian action to halt attacks onIsraelis by radical militants.

If the land-for-security deal can be concluded, the two sides have said they will immediately launch into overdue negotiations on the Palestinians' ultimate goal -- creation of an independent state in the West Bank and Gaza Strip with at least part of Jerusalem as its capital.

If the talks fail, Arafat has warned he intends to unilaterally declare the creation of a state in May 1999, when interim peace accords with Israel expire. Netanyahu has countered that he will impose harsh sanctions on the Palestinians to block any such initiative.

There were indications that a deal was finally in view following nearly two years of acrimony, deadlock and distrust between Netanyahu's Right-wing government and the Palestinians.

Senior Palestinian officials said preliminary negotiations in Tel Aviv on Tuesday had virtually wrapped up an agreement on the central issue of Palestinian guarantees to protect Israelis from violent radicals.

``A good understanding has been reached on thesecurity issue,'' one senior Palestinian official said on condition of anonymity. Netanyahu confirmed the progress in talks on Wednesday with Jordan's Crown Prince Hassan, according to Jordanian officials who briefed Arafat's Palestinian Authority on the meeting.

Earlier in London, Arafat sounded uncharacteristically upbeat about the prospects of a deal in Washington. ``I am optimistic because of the energy and time invested by President Clinton,'' he said.

``It's a window of opportunity not only for them and for us, but for the entire Middle East,'' he said.

US officials however remained cautious, noting that the past months had seen many premature reports of a possible breakthrough.

Netanyahu, who came to power in June 1996 as the head of a fragile coalition of ultra-nationalist, religious and other Right-wing parties, has frozen implementation of limited autonomy agreements signed with the Palestinians by Israel's previous Labour government.

Netanyahu justified his decision to block scheduledfurther transfers of West Bank land to Palestinian rule by charging that the Palestinians had failed to honour their commitment under the peace accords to halt attacks on Israelis from land placed under their control.

After months of intense US pressure, Netanyahu finally agreed to a limited withdrawal from another 13 per cent of the West Bank, bringing the total area under full or partial Palestinian rule to 40 per cent, on the condition that the Palestinians meet his security demands.

The chances for ending the stalemate this week appeared to be jeopardized when suspected Palestinian militants killed one Israeli and seriously wounded another on Tuesday in an attack outside Jerusalem -- the latest in a series of deadly assaults by radicals opposed to the peace process.

Netanyahu resisted calls from the far Right in his government to cancel this week's negotiations in response to the killings.

But US officials remained wary of everyone's intentions given the atmosphere of distrust which has developedbetween the two erstwhile peace partners over the past two years.

In an effort to prevent harmful sniping during the negotiations, the State Department has attempted to impose what spokesman James Rubin described as a news ``brown out'' surrounding the negotiations.

Journalists will be barred from the negotiations at the isolated Wye River Conference Center and Rubin will handle the formal briefings for the press.

The State Department even reportedly attempted to discourage Israeli and Palestinian delegates from bringing cellular telephones to the talks fearing they would leak manipulative reports on the negotiations to journalists.

Even though the two sides have apparently neared agreement on the two core issues of the negotiations, numerous secondary matters could prove to be deal-breakers, officials said.

These include the scope and nature of a second interim Israeli re-deployment in the West Bank required by the peace accords, the release of Palestinian prisoners and the opening of transitcorridors for Palestinians between the West Bank and Gaza Strip.