Brown, seen as less hawkish than outgoing premier Tony Blair, said he believed that the Iranian nuclear row could be settled through "multi-lateral pressure."

Speaking in Bristol, western England, at a hustings event for the Labour party leadership, which he has already won, and deputy leadership, Brown was pressed on whether he would rule out military action.

But he would not give such an assurance, the broadcaster said.

The Press Association news agency reported Brown had called for a "peaceful settlement" to the situation and replied that multilateral action and economic sanctions were the best way forward when asked about the military option.

The United States has not ruled out taking military action against Iran over the disputed nuclear programme, while Britain has said that the use of force is not on the agenda.

Last week, Washington threatened new UN sanctions after the UN's International Atomic Energy Agency found that despite earlier measures, Iran continues to enrich uranium.

Iran denies any suggestion that it wants to develop nuclear weapons and insists its programme is for peaceful purposes.

Brown is due to replace Blair, who has stood shoulder-to-shoulder with the United States in neighbouring Iraq, on June 27.