Two days of talks in Paris between Iranian and European delegations about Iran's nuclear program ended late Saturday without a formal agreement, but diplomats said progress had been made.

"After two days of very difficult discussions, we have made significant progress toward a provisional agreement," a senior Iranian envoy involved in the negotiations said on condition of anonymity in a telephone interview from Paris. "We all agree after these difficult talks on a common approach to the problem. . . . An agreement is attainable."

A nearly identical statement from the French Foreign Ministry, issued after 20 hours of intense negotiations, also noted "considerable progress."

The European delegation -- with members from Britain, France and Germany -- and the Iranians will consult with officials in their capitals over the next few days and then provide formal responses. No further meetings are envisioned, the Iranian envoy said. European envoys stressed that Iran must answer by the time the International Atomic Energy Agency takes the issue up Nov. 25.

The Europeans are trying to persuade Iran to suspend its uranium enrichment program indefinitely as a way to ensure that it does not use the technology to produce a nuclear weapon. Iran has insisted that the suspension be no longer than six months and on assurances that it would not be asked to permanently revoke its right to have a nuclear energy program, according to European envoys.

Iran has said its uranium enrichment facility is part of a peaceful nuclear fuel program. But the scale of its efforts, conducted in secret over 18 years, has left U.S., European and Israeli officials suspicious that Iran is ultimately seeking to produce a nuclear weapon.

The Europeans have offered Iran diplomatic and economic incentives to suspend nuclear work that could lead to producing a bomb. If no agreement is reached, the Europeans will join the United States in referring Iran to the U.N. Security Council, which could impose economic sanctions.

Throughout the negotiations, the Europeans have faced pressure from the Bush administration, which has made clear its preference to take the issue to the Security Council.

China signaled Saturday that it opposed any U.S. effort to take Iran to the council, a potential blow to the Bush administration's goal of pressuring Iran.

The Chinese foreign minister, Li Zhaoxing, on a two-day visit to Iran, said at a news conference in Tehran that he had informed Secretary of State Colin L. Powell and British Foreign Secretary Jack Straw that confronting Iran at the United Nations would complicate efforts to find a solution.

China, which last month signed a multibillion-dollar gas deal with Iran, instead wants the issue settled at a lower level by the International Atomic Energy Agency, the U.N. nuclear watchdog, Li said.

"I told all my colleagues that China supports a solution to this issue within the framework of the International Atomic Energy Agency," Li told reporters. Taking it to the Security Council "would only make the issue more complicated and difficult to work out," he said.

China, one of five members of the Security Council that wield veto power, holds a critical card in the looming debate about Iran's nuclear program. Iran and China have developed increasingly close ties, and China now receives about 17 percent of its oil from Iran and is rapidly becoming one of its largest trading partners.

Linzer reported from New York. Correspondent Glenn Frankel in Paris contributed to this report.

Chinese Foreign Minister Li Zhaoxing, left, talks to Iranian President Mohammad Khatami in Tehran. China is increasing its trade with Iran.