The announced reconciliation on Wednesday between Fatah and Hamas, the estranged Palestinian movements, puts the Obama administration in the uncomfortable position of having to reconsider its financial support for the Palestinian Authority, including millions of dollars the United States has spent to train and equip Palestinian security forces, officials and members of Congress said.

The agreement, reached after secret talks brokered by Egypt, caught the Obama administration, like many others, by surprise. At a minimum it complicates the administration’s faltering hopes to revive Israeli-Palestinian peace talks. It also casts doubt on American efforts in recent years to build up the Palestinian Authority on the West Bank, led by Fatah, as the legitimate leader of the Palestinians.

The White House, which has been debating how best to revive peace talks ahead of an address to Congress next month by Prime Minister Benjamin Netanyahu, all but dismissed the proposed reconciliation by reiterating the longstanding American designation of Hamas as a terrorist organization that has never expressed a willingness to recognize Israel, let alone negotiate with it.

“As we have said before, the United States supports Palestinian reconciliation on terms which promote the cause of peace,” Tommy Vietor, a spokesman for the National Security Council, said in the administration’s only public response. “Hamas, however, is a terrorist organization which targets civilians.”

He added that any Palestinian government had to accept certain principles announced by international negotiators known as the Quartet: the United Nations, the European Union, the United States and Russia. They include renouncing violence, abiding by past agreements with the Israelis and recognizing Israel’s right to exist. Hamas has never agreed to those conditions.

Administration officials declined to discuss publicly the impact the reconciliation might have on American policy, saying they were still trying to learn more about how exactly the two rival organizations would be able to reunite years after violently splitting.

There were, however, immediate calls by pro-Israeli members of Congress to withhold American aid to the Palestinians if their leadership included Hamas. “It calls into question everything we have done,” Representative Gary L. Ackerman, Democrat of New York, said in a telephone interview. He later issued a statement saying the United States would be compelled by “both law and decency” to cut off all aid.

“I don’t think there is any will on the part of the administration or the Congress to provide funds to a government that is dominated by a dedicated terrorist organization,” he said.

The administration is already on record warning of that. Shortly after taking office, Secretary of State Hillary Rodham Clinton flatly ruled out cooperating with a Palestinian Authority that included Hamas as a partner.

“We will not deal with, nor in any way fund, a Palestinian government that includes Hamas unless and until Hamas has renounced violence, recognized Israel and agreed to follow the previous obligations of the Palestinian Authority,” she told Congress then.

Since 2005, under President George W. Bush, the United States has spent $542 million to train the Palestinian Authority’s National Security Force, provide it nonlethal equipment and refurbish its camps and buildings. That included $150 million in the current fiscal year. That training, while viewed with suspicion by some of Israel’s supporters, has been credited with improving the professionalism of the forces and security more broadly.

Similar military aid given to Lebanon since 2006 was blocked by Congress after suspicions that parts of the Lebanese Army had allied with members of Hezbollah, also designated a terrorist group.