Bush telephoned the leaders of Germany and Italy, while US Secretary of State Condoleezza Rice called her Russian and German counterparts as well as EU foreign policy chief Javier Solana, US officials told reporters.

Iran appears headed for a showdown with the UN Security Council, which is expected to use an August 31 meeting to take up Tehran's refusal to freeze uranium enrichment and reprocessing activities as demanded by world powers.

"There is still time before August 31 for Iran to comply," US State Department acting spokesman Gonzalo Gallegos told reporters. "We encourage Iran to make the right choice."

The United States and other world powers have reacted coolly to Iran's response to a package of incentives offered by the five permanent Security Council members and Germany -- colloquially known as "P5 plus one" -- in return for a moratorium on sensitive uranium activities.

"Their response fell short," White House spokeswoman Dana Perino told reporters as Bush traveled here to his parents' oceanside compound for a weekend family wedding.

"Security Council Resolution 1696 has the deadline of August 31st, and so the members of P5 plus one are going to be discussing and communicating amongst themselves, reviewing the response from Iran and then meeting on August 31st, as spelled out in that resolution, as well," said Perino.

"We are looking at the August 31 date and once we get there we'll begin to take action," Gallegos said in Washington. "We are working with the UN Security Council to do this in an expedited manner."

In his conversations with German Chancellor Angela Merkel and Italian Prime Minister Romani Prodi, Bush "discussed diplomatic efforts to prevent Iran from acquiring nuclear weapon capability," said Perino.

He also discussed efforts to assemble a multinational force for Lebanon to enforce a fragile ceasefire, the spokeswoman said.

There were no other details from Rice's telephone conversations with German Foreign Minister Frank-Walter Steinmeier and Russian Foreign Minister Sergei Lavrov.

Washington accuses Tehran of using a civilian nuclear program as cover for a quest for atomic weapons. The Islamic republic denies the accusation.

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