We've known this all along, of course, but to watch the change in policy in action is breathtaking to behold. Both Bill Clinton and George Bush made it plain that a nuclear Iran was "unacceptable." Obama gave lip service to that idea for a little more than a year until it became apparent that he would be unwilling to move on Iran without the backing of the Security Council. Since China and Russia have no desire to see their business interests damaged by a US attack on Iran, Obama has dropped the idea of stopping them altogether and is now seeking a way to live with an Iran armed with nukes.

Greg Sheridan:

Obama has not explicitly announced his new position and he and his cabinet secretaries still make speeches saying they will try to prevent Iran acquiring nuclear weapons. But if you look at the statements closely you see a steady weakening of resolve, a steady removal of any threat of any consequence for Iran. Similarly, if you look at the actions of the administration, the sombre conclusion is inescapable.

Given Iran's missile program, which has no conceivable military use except to carry nuclear weapons, and which can now reach Europe and in due course will have a longer range, the fundamental change in US policy has global security consequences.

It has global security consequences in other ways, as well. It profoundly undermines American strategic credibility, which is the bedrock of whatever global order this troubled planet enjoys.

The troubling realisation that the Americans have given up, or are in the process of giving up, the fight to prevent Iran going nuclear is backed by the best informed security sources in Washington, London, Jerusalem and Canberra.

The bust-up between Washington and Israel only makes sense in this context. Last week, Israel's Prime Minister Benjamin Netanyahu met Obama in the White House, and also met Secretary of State Hillary Clinton at the State Department. On both occasions, all photographers and all TV cameras were banned. This was a studied humiliation of Netanyahu and all, ostensibly, because Israel announced that in three years' time 1600 apartments would be built in a Jewish neighbourhood in East Jerusalem.

The pressure we are putting on Israel to deal with the Palestinians is part of this idea that we can deter Iran through negotiations. It is a article of faith in the Obama administration that the cause of all problems in the middle east - including Iran's nuclear program - is that Israel refuses to make peace with Hamas. The idea that even if Israel was pressured enough into national suicide that Iran would magically drop its nuclear ambitions is the kind of thinking that is going to blow up half the world.

A nuclear armed Iran would represent an incredible danger. Accepting that level of threat to us or our allies and friends shows Obama to be deluded about Iran to the point of arrogance. If he actually believes that he can stop the Iranians with a few meaningless sanctions, he may go down in history as the man who enabled the Iranian nuclear bomb..