WASHINGTON (Reuters) – Brazilian President Luiz Inacio Lula da Silva’s visit to Iran this weekend may be the last chance to engage Iran over its nuclear programme before fresh UN sanctions, a senior US official said yesterday.

The official, who spoke on condition that he not be named, said President Barack Obama has not given up on seeking a diplomatic solution but Washington has concluded Tehran will not curb its nuclear ambitions without further sanctions.

The United States and some of its allies accuse Iran of seeking to use its civilian nuclear programme as a cover for pursuing nuclear weapons. Iran denies this, saying its programme is solely to generate electricity.

Brazil and Turkey, which hold rotating seats on the UN Security Council, have talked to Iran to try to revive a moribund agreement under which it would would send low-enriched uranium abroad and receive a higher grade uranium in return.

“I think we would view the Lula visit as perhaps the last big shot at engagement,” the senior US State Department official told reporters.

US officials stress in public that they support Brazil and Turkey’s efforts while saying in private that should these fail, they hope countries will be more disposed to imposing a fourth round of UN Security Council sanctions against Iran.