Prime Minister Tony Blair said Thursday that British officials were investigating evidence that Iran may have supplied sophisticated bombs to insurgents in Iraq. He warned Iran that "we're not going to be intimidated."

At a joint news conference with Iraqi President Jalal Talabani, Blair stressed that "we cannot be sure" Iran provided the devices, but that the British government had "certain pieces of information that lead us back to Iran" or to Hezbollah, the Iranian-backed militia in Lebanon.

Iranian officials denied the allegations, which were first made Wednesday by an anonymous British official who told British reporters that the bombs had killed eight British soldiers since May.

Speaking on Iranian television, Hamid Reza Asefi, the spokesman for Iran's Foreign Ministry, said: "This is a lie. The British are the cause of instability and crisis in Iraq," the BBC reported.

President Bush also delivered a warning to Iran on Thursday, saying in a speech that "state sponsors like Syria and Iran have a long history of collaboration with terrorists and they deserve no patience from the victims of terror."

In Baghdad, a senior U.S. military official who spoke on condition of anonymity said that technology for the bombs, known as shaped charges, came from Iran. But he expressed doubt that the Iranian military provided the technological know-how.

Fifty-eight such bombs have been found in Baghdad alone since April, the official said.

The bombs are used both by Shiite and Sunni Muslim insurgent groups, he said. They include Moqtada Sadr's Mahdi Army militia, which Britain and the United States have blamed for deadly bombings of U.S. and British convoys in the southern city of Basra.

Blair's warning adds to already heightened tension between Britain and Iran over the Islamic republic's nuclear ambitions. Britain, France and Germany, supported by the United States, negotiated unsuccessfully to persuade Iran to permanently stop elements of a nuclear program that could produce material for weapons. Iran's president, Mahmoud Ahmadinejad, has strongly asserted his country's right to undertake what he describes as a civilian nuclear power project.

The board of the International Atomic Energy Agency passed a resolution last week saying that Iran violated treaty obligations by secretly developing a nuclear program. That could eventually lead to the U.N. Security Council considering sanctions against Iran.

On Tuesday, Iran offered to return to talks, but only with no conditions. The Europeans have said that Iran must first suspend uranium conversion.

Blair said that if Iran was "trying to make some point about the negotiations over the nuclear weapons issue" by supporting the Iraqi insurgency, Britain was "not going to be intimidated."

Appearing at Blair's side at 10 Downing Street, the prime minister's office, Talabani said that officials in his government had raised the issue with their "Iranian brothers" and they had denied involvement. He quoted Iranian officials as saying, "We are not doing anything against Iraqi people, or against multinational forces, because we want to see Iraq stable, and we are not ready to bring our differences with the U.S. to inside Iraq."

Speaking just ahead of next week's key referendum on a new Iraqi constitution, Talabani said it was critical that British and U.S. troops remain in Iraq.

Talabani urged Blair not to give in to pressure for a timetable on withdrawing troops, and Blair said British forces would remain in Iraq as long as the Iraqi government wanted them there.

Speaking in English, Talabani thanked Blair and the families of British soldiers for Britain's role in "liberating us from the dictatorship" of Saddam Hussein, the ousted president of Iraq. "Saddam's Iraq was a concentration camp above ground and a mass grave beneath it," Talabani said. "Your sons and daughters freed us from that nightmare."

Knickmeyer reported from Baghdad.

Iraqi President Jalal Talabani said Iran had denied providing bombs.