Britain was seriously concerned about Iran's uranium enrichment activities, Foreign Secretary Jack Straw said in a statement on Wednesday.

"The latest Iranian statement further undermines international confidence in the Iranian regime and is deeply unhelpful," the statement said, adding "it is contrary to repeated requests by the IAEA Board and now by the Security Council that Iran resume full and sustained suspension of all enrichment and reprocessing activities, including research and development."

Straw urged Iran to suspend its atomic work immediately and return to talks.

"The Iranian regime must demonstrate by its words and actions that it is not seeking nuclear weapons," Straw said.

"If Iran does not comply, the Security Council will discuss further diplomatic measures," said Straw.

"We will remain in close contact with our international partners, whose strong reactions show the depth of international concern ... about Iran's activities," Straw added.

Iranian President Mahmoud Ahmadinejad announced on Tuesday that Iran had successfully enriched uranium, but stressing that it did not want to seek to develop nuclear weapons.