Palestinian President Mahmoud Abbas agreed to resume direct negotiations with Israel only after intense pressure from the United States and Europe, diplomats said Friday, as the Obama administration sought to restart the Middle East peace process but left many key questions unanswered.

WASHINGTON — Palestinian President Mahmoud Abbas agreed to resume direct negotiations with Israel only after intense pressure from the United States and Europe, diplomats said Friday, as the Obama administration sought to restart the Middle East peace process but left many key questions unanswered.

In announcing the new talks Friday, Secretary of State Hillary Rodham Clinton said the negotiations would cover all the issues that had bedeviled peace negotiators since 1979: the status of Jerusalem, the borders of a Palestinian state, the right of return for Palestinian refugees who were forced to leave their homes, and security provisions for Israel. She did not mention a basic plank of previous talks: using Israel’s pre-1967 borders as a basis for territorial negotiations.

Nor did the Obama administration announcement mention a set agenda, a plan for which issues would be tackled first or basic terms of negotiations. Neither Clinton nor the administration’s Middle East envoy, George Mitchell, mentioned whether Israel would agree to extend a moratorium on the construction of Jewish settlements, which Palestinian advocates had indicated was a crucial requirement to the success of any peace deal, and which Abbas had previously demanded as a condition to talks.

The chief Palestinian negotiator, Saeb Erekat, said that if Israel announced new settlement construction, the Palestinians would withdraw.

Middle East experts said the lack of specificity in Clinton’s announcement and the lack of any public signal by Israeli Prime Minister Benjamin Netanyahu that he would make any concessions, could prove perilous domestically for Abbas, who is already the politically weak leader of a divided people. As a result, analysts said, Abbas is coming to the table reluctantly. Abbas made no public statement endorsing the scheduled talks Friday.

Daniel Levy, a former Israeli peace negotiator, said: “Abbas wanted a clear reference to the 1967 lines; instead he was given 12 months to continue making his case in the hopes that the Americans will intervene decisively.” Arab diplomats offered a similar analysis.

Under the agreement that set up the yearlong talks, Obama will hold separate discussions with Netanyahu and Abbas on Sept. 1 and host them at a White House dinner, which will also be attended by Egypt’s President Hosni Mubarak and Jordan’s King Abdullah II.

Egypt and Jordan will play a crucial support role in the new talks. Also invited is former British Prime Minister Tony Blair, the special representative of the “Quartet” of Mideast peacemakers: the U.S., the U.N., the European Union and Russia.

On Sept. 2, Clinton will bring Abbas and Netanyahu together for the first formal round of direct talks since December 2008. At that point the parties will decide where and when to hold later rounds and lay out what is to be discussed.

U.S. diplomats, their European counterparts and Obama made the case to Abbas to return to the negotiating table without conditions, administration officials and Arab diplomats said. U.S. officials said they could do more to help the Palestinian cause through direct negotiations.

By setting a one-year deadline for the negotiations, the U.S. is implicitly giving Abbas the assurance that if the two sides cannot make progress soon, the United States will step in with its own proposal outlining what a peace deal should look like.

“We will be active and sustained partners, although we recognize that this is a bilateral negotiation,” Mitchell said at a State Department news conference.

Mitchell said the U.S. goal was “an agreement that will end the conflict for all time and will result in the establishment of a viable, democratic and independent state of Palestine living side by side in peace and security with Israel.” Asked what Hamas’ involvement would be in the talks, he said, “None.”

Hamas is a militant Iranian-backed Islamic organization that wrested control of the Gaza Strip in June 2007 after it won a majority of seats in January 2006 elections. Pledged to Israel’s destruction, it’s listed as a terrorist organization by the U.S., European Union and other countries.

Material from The Associated Press and the Tribune Washington bureau is included in this report.