WASHINGTON (AFP) - US President Barack Obama told Mahmud Abbas on Monday that the Palestinian leader and Israel's politicians must be prepared to make tough decisions and take "risks" for peace.

Abbas arrived at the White House two weeks after Israeli Prime Minister Benjamin Netanyahu, warning that time was running short for a final deal and saying Israel could show it was serious by honouring a scheduled release of Palestinian prisoners this month.

Obama, personally supporting Secretary of State John Kerry's exhaustive Middle East peace drive at a critical moment, is pressing both sides to accept a framework to carry negotiations past an end-of-April deadline.

"As I said to Prime Minister Netanyahu when he was here just a few weeks ago, I believe that now is the time... to embrace this opportunity," Obama said.

"It is very hard, very challenging. We are going to have to take some tough political decisions and risks if we're able to move it forward."

Obama said that everyone understood the shape of an "elusive" peace agreement between Israel and the Palestinians, saying it would be based on 1967 lines with mutual land swaps.

Abbas sat beside Obama in the same Oval Office chair recently used by Netanyahu, when the Israeli leader complained Israel had done its part over decades of peace talks and the Palestinians hadn't done theirs.

The white-haired Palestinian leader told Obama: "We don't have any time to waste.

"Time is not on our side, especially given the very difficult situation that the Middle East is experiencing and the entire region is facing."

Abbas did not use a photo opportunity before the talks to directly address the Israeli government's demand for the Palestinians to recognise Israel as a "Jewish" state in public.

But he did say through a translator that the Palestinians had recognised Israel's legitimacy in 1988 and in "1993 we recognised the state of Israel."

Palestinian negotiator Saeb Erekat said that "Abbas confirmed his position to President Obama refusing to recognise Israel as a Jewish State."

Abbas noted in the photo-op the agreement that the Palestinians have with Israel on the release of a fourth batch of prisoners by March 29.

"This will give a very solid impression about the seriousness of these efforts to achieve peace," Abbas said.

Israeli ministers said last week that they would have difficulty approving the prisoner release if agreement was not reached to extend the peace talks.

Israel committed to the release of 104 Palestinian prisoners in four tranches when talks were launched in July. It has so far released 78 of those in three batches.

Abbas spokesman Nabil Abu Rudeina said that Obama had not yet presented Abbas with a framework agreement.

But the US president did offer ideas to the Palestinian side, adding that discussions would continue in the coming weeks.

Ahead of the White House talks, thousands of Palestinians rallied in West Bank cities to show support for Abbas.

"We're here today to stand up to pressures upon us and make sure president Abbas adheres to his convictions," said Nasser Eddin al-Shaer, a former Palestinian education minister and member of Fatah's Islamist rivals Hamas, at a 5,000-strong rally in the northern West Bank city of Nablus.

Despite multiple trips to the region by Kerry, the two sides appear to have made little progress since the talks resumed in July after a three-year freeze.

Kerry and Abbas also met Monday.

"There were no formal proposals or positions on the table, but Secretary Kerry and his negotiating team will continue this process with both parties in the days ahead," a senior State Department official said.

The most nettlesome issues in the peace process include the contours of a future Palestinian state, the fate of Jerusalem and Palestinian refugees, Israeli settlements, security and mutual recognition.

The Palestinians want borders based on the lines that preceded the Six-Day War in 1967, when Israel captured the West Bank, including now-annexed Arab east Jerusalem.

They have also insisted there should be no Israeli troops in their future state.

But Israel wants to retain existing settlements it has built inside occupied Palestinian territory over the past decades.

It also wants to maintain a military presence in the Jordan Valley, where the West Bank borders Jordan.