By Jeffrey Heller

TEL AVIV, Israel (Reuters) - Israeli Prime Minister Benjamin Netanyahu flew to Washington on Sunday with the U.S. Middle East peace drive in crisis over a threat by Palestinian President Mahmoud Abbas to stand down.

Abbas's potential departure could mean the loss of a pivotal partner for Middle East peace talks, and it is likely to be the subject of discussions between President Barack Obama and Netanyahu when the two leaders meet on Monday.

An Obama administration official confirmed the meeting but would not say what was on the agenda. Aides to Netanyahu said the pair would discuss the peace process and the nuclear stand-off with Iran.

Spokesmen for Netanyahu said the main reason for his four-day trip, which will include a Paris stopover for talks with France's President Nicolas Sarkozy, was a speech on Monday to a forum of North American Jewish leaders in Washington.

Netanyahu aide Nir Hefetz rejected any suggestion of a chill in ties with Washington over obstacles in the way of Obama's goal of renewing peace talks, stalled since the Gaza war.

"It takes time to build personal relations, and I believe we are on the way to doing so," Hefetz said on Israel Radio.

Netanyahu has declined to comment on Abbas's announcement he will not stand in elections scheduled for January 24 -- a move that could keep peace talks on hold for months to come.

But, he told reporters traveling with him to Washington: "We are ready to talk and the Palestinians aren't. It's as simple as that."

"NOT EXCITED"

A moderate supported by the West, Abbas accused Washington of retreating from its demand for a freeze on Jewish settlements in the occupied West Bank before peace talks resume.

Israeli officials say Netanyahu wants to avoid interfering in Palestinian politics. But some commentators say the right-wing Israeli may be deliberately ignoring Abbas's threat, seeing it as just another bid to press Israel to halt settlement construction.

Netanyahu insists he needs to accommodate the needs of growing families in Israeli enclaves in the West Bank but has said Israel will avoid constructing any additional settlements.

Since taking office in March, he has repeatedly accused Abbas of delaying peace talks and setting new conditions. He has also introduced a new Israeli demand that the Palestinians recognize Israel "as a Jewish state."

Israeli Foreign Minister Avigdor Lieberman, himself a settler heading an ultranationalist party, said he did not take Abbas's threat seriously.

"You could call it an exercise, or a threat," Lieberman said. "You can interpret it as you wish, but I wouldn't get very excited about it."

Israeli President Shimon Peres, a Nobel peace laureate for his role in the first Israeli-Palestinian interim accord in 1993, has been virtually alone in urging Abbas to stay on.

Addressing tens of thousands at a candlelit memorial for assassinated Israeli leader Yitzhak Rabin, Peres spoke of Abbas, saying: "I say to him as a colleague -- do not let go!"

(Writing by Allyn Fisher-Ilan, additional reporting by Ross Colvin in Washington; editing by Andrew Roche)