Iran 'one year from nuclear bomb'

Four senior representatives of Barack Obama's administration told Congress they were pursuing new sanctions on Iran urgently and that a military strike had not been ruled out.

President Obama has said he will not "take any options off the table with respect to Iran", under-secretary of defence Michele Flournoy said.

"Now, that means to me that military options remain on the table," Mr Flournoy said.

Iran is pursuing an aggressive missile programme, including intercontinental missiles that it would need outside expertise to perfect, Defence Intelligence Agency director Lt Gen Ronald Burgess told the Senate Armed Services Committee.

That is not the same as saying that Iran is closing in on the means to launch a nuclear attack on the US, but the comments were among the Obama administration's most precise public assessments of Iran's military abilities and intentions.

Once Iran had decided to build one bomb, it could amass enough highly enriched uranium to do so in as little as 12 months, said General James Cartwright, vice chairman of the Joint Chiefs of Staff.

He added that Tehran would still need additional time to test the weapon and make it usable against an enemy.

New nuclear nations generally need three to five additional years to make a usable weapon, General Cartwright said, but the timeline could be shortened if Iran should pursue a warhead and a missile or other delivery system at the same time.

Iran had spurned Mr Obama's diplomacy, said under-secretary of state William Burns.

"Iran's reckless intransigence has left us no choice but to employ a second tool of diplomacy: economic and political pressure," he said.

The US is leading a drive for more international economic sanctions on Iran.

Mr Burns predicted a sanctions resolution would emerge from the United Nations Security Council within weeks and that China would agree.

But the US wants tougher penalties than some of its fellow veto-holding members of the council and Mr Burns would not say how tough he expected the resolution to be.

Defence secretary Robert Gates said he thought there was progress towards a UN resolution that would both isolate Iran and serve as "a launching pad for more specific sanctions by individual countries".

But Republican senator John McCain said the United States had been a paper tiger, threatening Iran but never fully confronting it.

"We keep pointing the gun. We haven't pulled a single trigger yet, and it's about time that we did," Mr McCain said.

Opinions vary on how much damage a US or Israeli military strike could do to Iran's nuclear programme. US officials generally say that a strike on one or more known facilities would set the programme back a few years, but not stop it.

The US has also acknowledged that once a nation has sufficient nuclear scientific and technological prowess, it could rebound from nearly any assault on facilities used for bomb development.

Officials would not speak publicly about whether the United States had changed its nearly four-year-old assessment that Iran was not actively seeking a bomb.

The US government is preparing a new classified assessment of Iranian nuclear ability and intent. The document is likely to conclude that Iran is at least three years from having a fully usable bomb, which includes the time needed to test a weapon and attach it to a missile or other means to deliver it.

Iran claims that its accelerated nuclear programme is aimed only at producing energy.