US President Donald Trump's administration waded into the decades-old Israeli-Palestinian conflict on Tuesday as one of his top advisers held his first meeting with Palestinian president Mahmud Abbas. After five hours of talks with Israeli Prime Minister Benjamin Netanyahu in Jerusalem on Monday night, Jason Greenblatt met Abbas in Ramallah in the occupied West Bank. Details of their talks were not yet clear. US officials have described the visit by Greenblatt, Trump's special representative for international negotiations, as a fact-finding mission as the White House seeks a way forward in restarting long-deadlocked peace efforts. But it comes after Trump cast uncertainty over years of international efforts to foster a two-state solution to the conflict when he met Netanyahu at the White House last month. At that meeting, Trump broke with decades of US policy by saying he was not bound to a two-state solution to the conflict and would be open to one state if it meant peace. He has also sparked concern among Palestinians and others by pledging during his campaign to move the US embassy in Israel from Tel Aviv to Jerusalem, the status of which is one of the thorniest issues of the conflict. Trump has since backed away, with US officials saying the decision-making process was in the early stages on the issue. There have been mixed signals over how Trump will approach his efforts to restart negotiations, with the conflict having confounded US leaders for decades. Trump spoke with Abbas in their first phone call on Friday, inviting him to visit the White House soon. The US president has also asked Netanyahu to "hold back on settlements for a little bit" and there have been warnings that unilateral action by Israel such as moving to annex the West Bank would provoke a crisis with Trump's administration. There has been growing concern that Israeli settlement building is eating away at prospects for a two-state solution, the basis of years of negotiations. Settlements are seen as illegal under international law and a major stumbling block to peace as they are built on land the Palestinians see as part of their future state. - 'Possible to advance peace' - In a rare move, former US president Barack Obama, in the waning days of his administration, declined to veto a UN Security Council resolution condemning Israeli settlement building, allowing it to pass. Trump had called on Obama to veto the resolution. After Monday night's meeting, Netanyahu's office and the US embassy issued a joint statement saying he and Greenblatt discussed settlement construction and ways to reach peace. The two "reaffirmed the joint commitment of both Israel and the United States to advance a genuine and lasting peace between Israel and the Palestinians that strengthens the security of Israel and enhances stability in the region," the statement said. They also "continued discussions relating to settlement construction in the hope of working out an approach that is consistent with the goal of advancing peace and security." According to the statement, Greenblatt "reaffirmed President Trump's commitment to Israel's security and to the effort to help Israelis and Palestinians achieve a lasting peace through direct negotiations." The statement cited Netanyahu as telling Greenblatt he believed "it is possible to advance peace" while Trump is in the White House. Greenblatt himself wrote on Twitter that he had a "very positive and productive meeting" with Netanyahu during which they discussed the "regional situation, how progress towards peace with Palestinians can be made & settlements." Netanyahu has found himself caught between maintaining relations with Washington and holding together his rightwing governing coalition, with some pushing for immediate action. On Tuesday, pro-settlement members of the coalition sought to advance a bill to annex a large Israeli settlement east of Jerusalem of some 37,000 people called Maale Adumim. The bill was on the agenda for a ministerial committee meeting on Tuesday, but was put off for another week. Netanyahu has reportedly been seeking to delay the bill due to concerns over how it will affect US relations.