A day after Palestinian leaders signed what many called a landmark reconciliation accord, the antagonists in the protracted Israeli-Palestinian conflict and their international mediators in Europe staked out positions in a rapidly shifting political and diplomatic landscape on Thursday.

Secretary of State Hillary Rodham Clinton, travelling to Rome for a meeting focused on Libya, refused to slam the door on negotiations that could include Hamas as part of a larger Palestinian authority, even as Hamas’s leader, Khaled Meshal, said he was fully committed to working for a two-state solution.

But Mr. Meshal was in no mood for concessions. In an interview in his Cairo hotel suite, he declined to swear off violence or to agree that a Palestinian state would produce an end to the conflict — key demands of Israel, the United States and Europe. He defined his goal as “a Palestinian state in the 1967 lines with Jerusalem as its capital, without any settlements or settlers, not an inch of land swaps and respecting the right of return” of Palestinian refugees to Israel itself.

Asked if a deal honoring those principles would produce an end to the Israeli-Palestinian conflict, however, Mr. Meshal declined to elaborate. “I don’t want to talk about that,” he said.

He added: “When Israel made agreements with Egypt and Jordan, no one conditioned it on how Israel should think. The Arabs and the West didn’t ask Israel what it was thinking deep inside. All Palestinians know that 60 years ago they were living on historic Palestine from the river to the sea. It is no secret.”

None of Thursday’s statements suggested an imminent breakthrough in the Israeli-Palestinian situation; on the contrary. But the subtle shifts in tone — if not substance — underscored the degree to which the newest Palestinian attempt at reconciling embittered rivals in Gaza and the West Bank has changed the dynamic of a conflict that has been at an impasse for years.

Plans for President Obama to lay out broad proposals for a peace process this week — the subject of debate within his administration — were scuttled after the Hamas-Fatah accord was announced last week, according to two people briefed on the plans. (The raid that killed Osama bin Laden in Pakistan early Monday cemented the decision to postpone the speech, one senior administration official said.)

The administration has reacted warily to the reconciliation pact, with many expressing doubt it would survive even as long as a week, but pointedly officials have not rejected it outright, as Prime Minister Benjamin Netanyahu has. The senior administration official said that the United States, unlike in the past, did not want to preclude a genuine shift by Hamas, or force the Palestinians into a corner by denouncing any alliance that would include a group the United States and others designate as terrorists. “There is a calculated element to this,” the official said.

When asked if the reconciliation would close the door to any possible negotiations with the Israelis or force a suspension in security assistance the United States has funneled to the Palestinians in the West Bank since 2005, Mrs. Clinton declined to answer directly.

“There are many steps that have yet to be undertaken in order to implement the agreement,” she said. “And we are going to be carefully assessing what this actually means, because there are a number of different potential meanings to it, both on paper and in practice.”

She emphasized, as the administration has always done, that the United States would not accept a Palestinian government that included Hamas unless the group renounced violence, agreed to live by previous Israeli-Palestinian agreements and recognized Israel. These are the so-called “quartet principles,” agreed on by the United States, the United Nations, the European Union and Russia.

Prime Minister David Cameron of Britain made a similar point during a visit to London by Mr. Netanyahu, who later went on to Paris, reflecting the sudden diplomatic urgency caused by the reconciliation between Hamas and Fatah, the party that leads the Palestinian Authority in the West Bank.

The Palestinian Authority president, Mahmoud Abbas, for his part, travelled to Berlin to make the case for a declaration of Palestinian statehood, only to hear from Chancellor Angela Merkel that “unilateral steps” were not helpful. Mrs. Merkel urged a rapid return to peace efforts based on recognition of Israel’s right to exist, the renunciation of violence and commitment to the process of negotiation. “Time is short,” she said.

As those meetings unfolded, differences between France and Germany seemed to be widening, particularly over the question of whether the United Nations should endorse a declaration of Palestinian independence in September, as Palestinian leaders are urging.

In an interview published on Thursday, President Nicolas Sarkozy of France implied that he would support the idea of recognition if Middle East peace efforts remained stalemated through the summer.

Mr. Abbas, who has largely given up on peace negotiations with Israel under Mr. Netanyahu, concluded that the best way forward was national unity and an appeal to the international community to create a Palestinian state in the West Bank, Gaza and East Jerusalem.

Fatah and Hamas fought a brief civil war in 2007 and have been divided ever since. The agreement they signed this week calls for a new government of technocrats to plan for elections in the coming year as well as committees to coordinate security cooperation and questions like prisoner releases.

The bitterness runs deep, though, and many challenges remain. “The whole world knows what Hamas thinks and what our principles are,” Mr. Meshal said on Thursday. “But we are talking now about a common national agenda. The world should deal with what we are working toward now, the national political program.”

Asked whether in his pact, he had agreed to end violent resistance, he replied: “Where there is occupation and settlement, there is a right to resistance. Israel is the aggressor. But resistance is a means, not an end.”

He added that over the coming months that, as Hamas and Fatah worked out their differences, “we are ready to reach an agreement on how to manage resistance.”

He said that Hamas had entered into cease-fires with Israel in the past and that it was ready to do so in the future. There is one in effect right now. “If occupation ends,” he said, “resistance ends. If Israel stops firing, we stop firing.”