The Vice Chairman of the US Joint Chiefs of Staff, Admiral James Winnefeld, is on a secret visit to Israel as tensions rise over Iran's nuclear progress, Israel's army radio reported on Thursday.

The Israeli military itself refused to confirm the report, which said Winnefeld was in the country at the invitation of his counterpart, Deputy Chief of Staff Major General Yair Naveh.

It was not immediately clear when Winnefeld arrived, but he was expected to leave later on Thursday.

Army radio said the visit had been kept under wraps because of political sensitivities between Israel and Washington over how to handle Tehran's nuclear ambitions, which both parties believe is an attempt to build atomic weapons.

Tehran insists its programme is completely peaceful, but Israel has warned that a nuclear Iran would pose an existential threat and said it would take all necessary steps to prevent that from happening, including a pre-emptive military strike.

Next week, another senior US military official is due in Israel, the Ynet news website reported.

Lieutenant General Craig Franklin, currently the commander of the US Third Air Force, is to visit ahead of a joint military drill between the two armies which is due to take place next month, Ynet said.

Last week, Time magazine said the US had significantly scaled down the planned joint military exercise, reducing by more than two-thirds the number of US troops taking part in a move linked to disagreements over how to deal with Iran's nuclear programme.

Tensions between the two allies have grown in recent weeks over reports suggesting that Israel was mulling an attack on Iran without White House approval.