UK, Israel warn Iran over nuclear program

LONDON (Reuters) - Britain and Israel warned Iran on Tuesday that it faced tougher international sanctions if it failed to cooperate on its disputed nuclear program.

The United States, Britain, France and Germany are expected to ask Russia and China in talks on September 2 to consider a fourth round of U.N. sanctions, possibly targeting Iran's oil sector, if Tehran does not accept negotiations on its nuclear program.

"If there is no further progress immediately then I believe the world will have to look at stepping up sanctions against Iran as a matter of priority," British Prime Minister Gordon Brown said at a news conference in London with Israeli Prime Minister Benjamin Netanyahu.

The United States and its allies, including Britain, accuse Iran of trying to develop atomic weapons, while Iran says it only wants nuclear technology to generate electricity.

Asked about the prospect of Iran developing nuclear arms, Netanyahu said: "Time is running out, it is late in the day, but it is not too late."

"If the resolve of the responsible members of the international community is strong and firm, then however late the hour, the future can be secured and this is our preference," added Netanyahu.

The Israeli prime minister said a disputed election in June showed the administration in Tehran did not enjoy the support of the Iranian people and was "far weaker than meets the eye."

Israel is believed to have the Middle East's only atomic arsenal. It says that an Iranian bomb is a threat to its existence that it will not tolerate.

The United Nations Security Council has imposed three sets of sanctions on Iran, in December 2006, March 2007 and March 2008, targeting Iranian companies and individuals linked to the nuclear program.

Iranian officials have repeatedly refused to curb the nuclear program despite the threat of sanctions.

The Vienna-based International Atomic Energy Agency is due to release a report on Iran this week which is likely to strongly influence the international response.

A senior Vienna diplomat told Reuters that Iran has not expanded the number of centrifuges enriching uranium at its Natanz nuclear site since the end of May after increasing capacity steadily over the previous three years.

Relations between Britain and Iran worsened after Iran's June presidential election. Brown accused Iran of "repression and brutality" in crushing protests against the re-election of hardline President Mahmoud Ahmadinejad.

Iran's Supreme Leader Ayatollah Ali Khamenei has called Britain "the most treacherous" of Iran's enemies.

(Additional reporting by Sylvia Westall and Mark Heinrich in Vienna; Editing by Jon Hemming)