The US military's top officer headed to Israel today at a time of mounting international anxiety over Iran's nuclear intentions.

The arrival of the Chairman of the Joint Chiefs of Staff, Army General Martin Dempsey, comes as Israel has grown increasingly vocal about its impatience over the international community's failure to curb Iran's nuclear programme through sanctions.

Israel, like the West, believes Iran is developing nuclear weapons technology. Iran says its programme is intended for peaceful purposes.

In the past few weeks, the US and Europe have moved to step up sanctions against Iran, a top Iranian nuclear scientist was killed in a mysterious assassination, and Tehran has threatened to shut down a key channel for the world's oil supply.

The Israeli and US militaries, meanwhile, have postponed large-scale war games, in part to avoid aggravating growing tensions, Israeli defence officials said.

A former Israeli military intelligence chief stoked the growing jitters by contending Iran already has all the components to build a nuclear bomb.

"If the Iranians get together tonight and decide to secretly develop a bomb, then they have all the resources and components to do so," Amos Yadlin told the Maariv daily.

It was not clear whether Yadlin, was referring to the mechanical elements of a bomb, or implying the Iranians have sufficient weapons-grade uranium, a critical ingredient for bombmaking.

Still, his remarks reflect the prevalent view in Israel that Iran is on the cusp of producing a bomb - a view at odds with the American assessment that Iran will not have bombmaking capabilities for years.

US ambassador to Israel Dan Shapira portrayed Dempsey's visit as part of the ongoing co-ordination between the two allies and a reflection of Washington's "unshakeable commitment to Israel's security".

But looming large over all discussions is the threat of an Israeli military strike. Israeli analysts have speculated that in his meetings with Israeli military and political leaders, Dempsey will warn Israel against attacking Iran, fearing it would ignite a broad regional conflagration.

On Wednesday, Israeli Defence Minister Ehud Barak denied that Dempsey would carry such a message - and added that Israel was "very far" from deciding whether to strike.