BERLIN — Secretary of State Condoleezza Rice warned Iran today the "international community is united" in the dispute over its nuclear program, but a Tehran envoy defiantly rejected a U.N. call to reimpose a freeze on uranium enrichment.

Rice spoke after a meeting in Berlin among diplomats from the five veto-wielding members of the U.N. Security Council plus Germany over ways to press Iran to stop enriching uranium, which can be used for weapons. Iran says its program is peaceful.

The meeting follows agreement Wednesday by the 15-member Security Council to ask the U.N. nuclear watchdog, the International Atomic Energy Agency, to report back in 30 days on Iran's compliance with demands to stop enriching uranium.

In Vienna, Iran's chief representative to the IAEA, Ali Asghar Soltanieh, told The Associated Press that "it is impossible to go back to suspension."

"This enrichment matter is not reversible," Soltanieh said.

Rice said the Berlin meeting sends "a very strong signal to Iran that the international community is united."

But the comments hinted at the strains in the anti-Iran alliance, with the Chinese saying that "only peaceful means" must be used to push Tehran. The United States and Britain used tougher rhetoric.

KANDAHAR, Afghanistan — Taliban militants launched a rare attack on a coalition base in southern Afghanistan Wednesday, killing an American and a Canadian soldier and sparking fierce U.S.-led retaliation that left 32 insurgents dead in the bloodiest fighting in months.The attack came a day after at least 10 people were killed in two separate roadside bombings and reflected a growing intensity of militant assaults after the Taliban warned of a renewed offensive this year."Over the last five or six weeks there have been various proven attacks mainly at night by the Taliban on that base, but I think it is fair to say this is the largest we have seen thus far," British spokesman Col. Chris Vernon told reporters in Kandahar.The battle began hours after Taliban insurgents ambushed an Afghan supply convoy as it returned to the remote forward operating base late Tuesday, killing eight Afghan soldiers, Vernon said.