OVER THE NORTH SEA, Oct 25 (Reuters) US Defense Secretary Robert Gates today characterized US military planning for a strike on Iran as ''routine''.

''I would characterize it as routine,'' Gates told reporters on a flight en route to Washington, when asked about any US planning for military action against Iran.

The Pentagon plans for hundreds of potential scenarios that could involve military force in a variety of roles ranging from offensive operations to disaster response.

Tensions between Washington and Iran have climbed this year.

The United States and others accuse Tehran of seeking nuclear weapons under cover of a peaceful nuclear energy program.

The United States also accuses Iran of providing weapons, training and other support to insurgents in Iraq.

Iran has denied those charges.

Gates said the United States was focused on diplomatic and economic pressure against Iran.

''The focus that we all have is on using diplomatic pressure and economic sanctions to persuade the Iranian government that they are isolated, they need to alter their policies and ambitions,'' he said.

Reuters SZ VP0058