Prime Minister Tony Blair (search) said Thursday that Iran (search) should be referred to the U.N. Security Council if it breaches its nuclear obligations, while Tehran vowed to resume some activities that can be part of the process of making nuclear weapons.

Hasan Rowhani, Iran's top nuclear negotiator, said negotiations with key European powers were not balanced and were costly for Tehran.

"Continuation of negotiations in their present format is not possible for us," Rowhani told Iranian state-run television. "The basic point that the Islamic Republic of Iran will resume part of its nuclear activities in the near future is definite."

Diplomats close to the International Atomic Energy Agency (search) and familiar with Iran's nuclear dossier said Rowhani appeared to be creating some wiggle room for his country in negotiations as his statement appeared more vague than other recent Iranian pronouncements warning such a move would come in the next few days.

Blair stepped up the pressure, warning that he would support Iran being referred to the U.N. Security Council, which could impose sanctions, if it breached its nuclear obligations.

"We certainly will support referral to the U.N. Security Council if Iran breaches it undertaking and obligations," Blair said at the first news conference since his Labour Party won a historic third term in last week's elections.

Iran suspended uranium-enrichment activities as a gesture of good faith in November and any resumption of conversion would likely torpedo talks with France, Germany and Britain, which are acting on behalf of the 25-nation EU.

Those talks are intended to ease suspicions about Tehran's ultimate nuclear aims. The United States says Iran wants to make a nuclear bomb, but Iran insists it is interested only in a source of energy.

Earlier in Vienna, Austria, a diplomat told The Associated Press that Iranian government officials in Tehran were discussing keeping their freeze on uranium conversion — at least over the next few days — because of a European warning that anything else would result in "consequences ... that would only be negative for Iran" — diplomatic code for likely action by the U.N Security Council.

Blair stressed that Britain was committed to the diplomatic process.

"Nobody is talking about invasions of Iran or military action against Iran. We have to make sure that this diplomatic process works, and we will fight very hard to do that. There is no point in speculating what happens down the line if you reach an impasse. But there is a lot of processes that have to be gone through before you are at that point, not least the Security Council," he said.

Iranian officials have indicated that they will resume uranium reprocessing work at the Isfahan Nuclear Conversion Facility in central Iran. The facility converts uranium ore concentrate, known as yellowcake, into uranium gas, the feedstock for enrichment.

Rowhani confirmed receiving messages from Europeans urging Iran not to resume such activities but said Tehran had made its decision.

"The principle that we resume activities has been decided. We are discussing the conditions and timing of that," Rowhani said.

Supreme Leader Ayatollah Ali Khamenei, according to state-run TV, said Iran was opposed to nuclear weapons but would not be "bullied" by the West into giving up its nuclear capabilities.

The various signals out of Tehran, which repeatedly has insisted it has a right to enrich uranium and conduct related activities including conversion, left officials at the IAEA guessing about Iran's intentions.

One diplomat close to the agency said the U.N. watchdog agency had expected formal notification that conversion activities would restart on Thursday. And Sirous Nasseri, a senior Iranian envoy confirmed hours after arriving in Vienna on Wednesday that he was carrying a letter from his government to the agency.

While he declined to disclose the contents of his letter, diplomats said it likely contained word of Iran's intention to resume conversion as part of a process whose end result is uranium hexafluoride — a substance that can be turned into either energy producing uranium or more highly enriched weapons grade material. The diplomats spoke on condition of anonymity because of the sensitivity of the issue.

Washington has long maintained that Iran's nuclear program — kept secret for nearly two decades until revealed by a dissident group in 2002 — is meant to make weapons, and as such, Tehran's nuclear dossier belongs in the hands of the Security Council. But because of strong resistance at previous IAEA board meetings, it reluctantly embraced the European diplomatic efforts.

The on-off talks, which began last year, have failed from the beginning to find common ground on the European insistence that Iran scrap — or at last agree to a long-term suspension of — uranium enrichment and related activities, and Tehran's insistence that any freeze was voluntary and short-lived. The last formal round ended inconclusively April 29.