The Bush administration said today that it had received word that Iran had recently arrested some Al Qaeda members operating in its territory, but that the actions had failed to ease American concerns about Iranian support for terrorist activities.

"The steps that the Iranians claim to have taken in terms of capturing Al Qaeda are insufficient," Ari Fleischer, the White House spokesman, said, after news reports of the arrests from Tehran. "It is important that Iran live up to its commitments and obligations not to harbor terrorists."

Administration officials said it was unclear how many Al Qaeda members had been arrested in Iran, what their identities were and whether they included any of the top officials, who some believe have been functioning with Iranian acquiescence.

Still, they said the arrests had failed to meet the demands that Al Qaeda members not simply be arrested but also handed over to Saudi Arabia or other authorities investigating the bombing of three foreign compounds in Riyadh earlier this month.

Despite the generally tough tone on Iran, however, administration officials said a high-level interagency meeting that had been scheduled for today to decide possible new punitive steps against the Tehran government had been postponed, in part to study the arrests and other developments.

The officials said the information about the arrests needed to be squared with other intelligence on Iran, and also with information from other countries that have an intense interest in Iranian behavior, including Britain and Pakistan.

Mr. Fleischer, dismissing Iran's actions on terrorism, also took a tough position on Iran's nuclear program, which the government in Tehran says is for peaceful purposes.

"The United States rejects that argument as a cover story," Mr. Fleischer said. "Our strong position is that Iran is preparing, instead, to produce fissile materials for nuclear weapons. That is what we see."

American officials said they were also studying official comments in Moscow that Russia was also trying to persuade Iran to keep its nuclear program peaceful, especially the Russian-financed reactor at Bushehr, which the United States says could be used to make weapons-grade plutonium.

Mr. Fleischer, referring to American pressure on President Vladimir Putin to act against Iran, said the United States remained "hopeful that we can effect a change in policy by Russia, but it does remain a matter of some dispute."

Administration officials say there is a split in the administration over how to proceed with Iran, with some advocating tough measures like cutting off diplomatic contacts and possibly supporting antigovernment opposition groups based in American-occupied Iraq.

Earlier this month, a scheduled meeting between Iranian and American officials was canceled. Instead, the United States sent a tough demand on Al Qaeda. Some officials were said to favor that those meetings, which have been going on for more than a year, be cut off.

Today, Secretary of State Colin L. Powell sought to play down the divisions. "Our policies with respect to Iran have not changed," Mr. Powell said following a meeting with the president of Madagascar. "We do not approve of their support of terrorist activities. We have made it clear over the years that we disapprove of their efforts to develop a nuclear capability."

Going further, Richard A. Boucher, the State Department spokesman, dismissed the idea that the United States was close to breaking off diplomatic contact — there have been no formal relations since the Iranian revolution more than two decades ago.

"We have ways of communicating, we have ways of contacting them, and we would expect to do so again," Mr. Boucher said.

The day's developments were a reminder of the fluid nature of American policy in the Middle East in the weeks following the war with Iraq. Some officials said the meeting on Iran due today was put off in part because of a separate preoccupation: planning President Bush's trip to the region next month.

American officials say their priorities toward Iran have been to stop its nuclear weapons program by using a combination of diplomacy and implied threat of force and to try to end Iran's support of terrorist groups.

On terrorism, the main concern has been Iran's support of Hezbollah, which has carried out attacks on Israel and other Western targets, often from bases in Syrian-controlled Lebanon.

Al Qaeda is believed to have operated in different parts of Iran, notably in the north and also in the barren southern mountains of Baluchistan, on the Pakistan border. Some American officials say that Iran has played host to Al Qaeda units that fled Afghanistan after the war there in 2002 and, more recently, from northern Iraq.

American officials say Iran has handed over Al Qaeda members in the past to Saudi Arabia and perhaps Pakistan, but there is disagreement on whether such steps were significant or sincere.

Meanwhile, Defense Secretary Donald H. Rumsfeld today cited another more recent problem that American officials have been worried about, Iran's support of Shiite groups in Iraq, which may be part of an effort to establish a Shiite theocracy in that country.

"Iran should be on notice: efforts to try to remake Iraq in Iran's image will be aggressively put down," Mr. Rumsfeld said at the Council on Foreign Relations in New York.