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 program before fresh U.N. sanctions, a senior U.S. official said on Thursday.
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 program as a cover for pursuing nuclear weapons. Iran denies this, saying its program is solely to generate electricity.
Brazil and Turkey, which hold rotating seats on the U.N. Security Council, have talked to Iran to try to revive a moribund agreement under which it 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 U.S. State Department official told reporters.
U.S. 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 U.N. Security Council sanctions against Iran.
"It's not that we've given up on engagement. We just remain skeptical that Iran is going to move on its own absent some additional pressure," the official said.
He said that if Tehran did not change its stance following Lula's visit "countries like Brazil, Turkey and others on the council should very definitely draw conclusions from that."
Lula is due to visit Iran on Sunday and Iran's Foreign Ministry has said Turkish Prime Minister Tayyip Erdogan was also expected to be in the Iranian capital on that day.
The U.S. official said there were some signs that Iran might try to arrange a broader meeting over the weekend, though he declined to say which nations might attend.
The Obama administration has accused Tehran of trying to buy time by accepting Brazil's offer to mediate and said Washington would be undeterred in its push for new sanctions.
U.S. Secretary of State Hillary Clinton spoke by telephone with Turkish Foreign Minister Ahmet Davutoglu and argued that Iran shows no sign of ceasing uranium enrichment as required by several Security Council resolutions.
Uranium enrichment can produce fuel for nuclear reactors or, if perfected, yield fissile material for atomic bombs.
State Department spokesman P.J. Crowley said if Iran did not change course after Lula's visit it should pay a price.
"At that point we believe that there should be consequences for a failure to respond," Crowley said.
Editing by Xavier Briand