The UN envoy for the Middle East peace process said on Wednesday that Jerusalem's future status must be negotiated between Israelis and Palestinians and warned of the repercussions of any action over the disputed city.
"The (UN) secretary general has spoken many times on this issue... and he has said that we all have to be very careful with the actions we take because of the repercussions of these actions," Nickolay Mladenov told a conference ahead of US President Donald Trump's plan to recognise Jerusalem as Israel's capital.
"The future of Jerusalem is something that needs to be negotiated with Israel, with the Palestinians, sitting side by side directly in negotiations.
"We are concerned about the possible escalation of tensions," foreign ministry spokesman Geng Shuang told a regular news briefing.
"All relevant parties should bear regional peace and tranquility in mind, be cautious in words and deeds, avoid impacting the foundation for the settlement of the issue of Palestine, and avoid causing new confrontation in the region."
"The President would say that the US government recognises that Jerusalem is the capital of Israel. He views this as recognition of historic reality," a senior Trump administration official told reporters.
"Jerusalem has been the capital of Jewish people since ancient times and the modern reality that it has been the seat of government, important ministries, its legislature, the Supreme court," the official said, speaking on condition of anonymity.
In taking this action, Trump will fulfil a major campaign promise that has been made by a number of previous presidential candidates, another senior official said.
Noting that finding appropriate land and construction of a new embassy would take at least a couple of years, officials said Trump would continue to give waiver as required by the Congress - for not moving its diplomatic mission to Jerusalem.
Trump's action enjoys broad bipartisan support in the Congress, the official said.
"Trump remains committed to achieving a lasting peace agreement between the Palestinians and Israel, and is optimistic that peace can be achieved," the official said, adding that not recognising Jerusalem as the capital of Israel has done nothing to achieve peace for more than two decades.
Trump recognises that the specific boundaries of Israeli sovereignty are subject to final status negotiations, the official said.
Trump has decided to go ahead with his plan, ignoring dire warnings from Saudi Arabia's King Salman and Egyptian President Abdel Fattah al-Sisi, one of his closest allies in the Middle East.
Terming it a "dangerous step", Salman cautioned the move will "provoke the feelings of Muslims around the world".
Sisi warned that the move will complicate the situation and "jeopardise the chances of peace in the Middle East".
Responding to questions, senior administration officials said the President believed that the move would have no impact on the peace process and the deal is within reach and can be achieved.
Earlier, Trump spoke over phone with a number of leaders in the Middle East to share his decision on Jerusalem, the White House said.
Trump spoke separately with Israel Prime Minister Benjamin Netanyahu, Palestine President Mahmoud Abbas, King Abdullah II of Jordan, Sisi and King Salman.
"This announcement does not change US policy over these specific borders," the senior administration official said, while another official asserted that the President is not taking a decision that affects any of the boundaries and sovereignty.
Trump's anticipated announcement received mixed message from lawmakers.
Senator Ted Cruz described this as a "historical" announcement.
"I strongly encourage and would unequivocally support President Trump formally recognising Jerusalem as Israel's capital and beginning the important process of moving our embassy from Tel Aviv to Jerusalem," he said.
Meanwhile, Senator Bernie Sanders said he was extremely concerned over Trump's plan.
"There's a reason why all past US administrations have avoided making this move, and why leaders from all over the world, including a group of former Israeli ambassadors, have warned Trump against doing it. It would dramatically undermine the prospects for an Israeli-Palestinian peace agreement, and severely, perhaps irreparably, damage the US' ability to broker that peace," Sanders said.
"What the US should be doing now is bringing adversaries in the Middle East together to seek common solutions, not exacerbating tensions in this highly volatile region," he said.
Meanwhile, the State Department warned US embassies around the world to prepare for possible protests and violence and banned travel by government employees and their families to Jerusalem's Old City and the West Bank.