Mahmoud Abbas also said he might opt to dissolve the Hamas-led government.
He said at a news conference with Sheikh Khalid Bin Ahmed Al-Khalifa, the Bahraini foreign minister, on Wednesday: "There is no dialogue now."
A preliminary coalition agreement between Abbas' Fatah movement and Hamas, announced on September 11, "is over now, and we have to start from square one," he said, not ruling out the renewal of talks at a later date.
Abbas also said a new Cabinet must be formed to end a recent surge in inter-faction fighting that has killed 10 people in three days. He did not elaborate, but Abbas holds wide-ranging constitutional powers that include the authority to disband the government.
"There are many bloody events now, and we need to end this crisis as soon as possible, reach a solution and form a new Cabinet," he said.
Asked if he would use his powers to dissolve the government, he replied: "My constitutional authority will be used at the appropriate time... We are going to see how to deal with the solution. All doors are open."
However, Hamas Cabinet minister, giving a different assessment of the situation, said the two sides were on the verge of forming a government, possibly one made up of professionals, not politicians.
Abdel Rahman Zaidan, the public works minister, taking issue with Abbas's view of the situation, said the two sides were in "the final stages" of forming a so-called national unity government.
"There are many bloody events now, and we need to end this crisis as soon as possible, reach a solution and form a new Cabinet"
"There is serious thinking within Hamas to form a national unity government which is composed of professionals, basically, not political faces," Zaidan said. "This government would not be headed by a Hamas leader."
If he were to disband the government, Abbas could either form a Cabinet of professionals, rather than politicians, or call new elections.
Abbas was speaking hours before a scheduled meeting with Condoleezza Rice, the visiting US secretary of state.
Clashes between Palestinian forces
soared tension over power struggle
Rice is on a regional visit partly aimed at bolstering Abbas in his power struggle with Hamas.
Hamas entered the agreement with Fatah under pressure from crushing Western economic sanctions that have generated widening protests against the government.
In Brussels, more than 100 former world leaders and politicians called on Wednesday for urgent international action to end Arab-Israeli conflict, warning that the Middle East faced its "worst crisis for years".
In a statement issued by the International Crisis Group, a Brussels-based think tank, they called for an international conference to agree the outlines of a comprehensive peace deal and prepare for detailed negotiations.
They also urged support for a national unity government in the Palestinian territories, where internal fighting has spiralled, resumption of aid to the Palestinian Authority and talks between Israeli and Palestinian leaders.
"If the Arab-Israeli conflict, with all its terrible consequences, is ever to be resolved, there is a desperate need for fresh thinking and the injection of new political will"
The International Crisis Group
"Everyone has lost in this conflict except the extremists throughout the world who prosper on the rage that it continues to provoke," said the 135 signatories, who included dozens of ex-presidents and prime ministers and seven Nobel laureates.
"Every passing day undermines prospects for a peaceful, enduring solution," said the statement, signed by Mikhail Gorbachev, the former Soviet president, Jimmy Carter, the former US president, and Desmond Tutu, the South Africa's Archbishop, among others.
The statement said the Quartet of Middle East peace negotiators should also hold talks with Israel, Syria and Lebanon to discuss the foundations of a wider peace.
"If the Arab-Israeli conflict, with all its terrible consequences, is ever to be resolved, there is a desperate need for fresh thinking and the injection of new political will," it said.