The leader of Britain's main opposition party on Sunday called on Prime Minister Tony Blair to spell out the danger to Britain from Saddam Hussein in order to rally support for military action against Iraq.

Writing in The Sunday Times newspaper, Conservative Party leader Iain Duncan Smith said he supported an attack on Saddam, whom he said had "the means, the mentality and the motive" to threaten Britain's security.

"It is now time for the prime minister to explain to the British people what he already knows -- that Iraq is a clear and growing danger to Britain," Duncan Smith wrote.

"That will mean leading the public debate and arguing from real principles, using every opportunity to put the case including a debate in Parliament" when it returns from its summer recess, he added.

Britain is regarded as the United States' strongest ally in the event of a military strike on Iraq. But Blair faces strong opposition to war from the public and within his own Labor Party.

On Saturday Blair stressed that he had not decided whether military action was the way to ensure Saddam readmitted United Nations weapons inspectors and did not maintain weapons of mass destruction.

"Doing nothing about Iraq's breach of these U.N. resolutions is not an option," Blair told reporters as he flew to Mozambique, according to Britain's Press Association news agency. "That's the only decision that's been taken so far. What we do about that is an open question."

The Ministry of Defense said Saturday that Defense Secretary Geoff Hoon would hold talks in Washington with Defense Secretary Donald H. Rumsfeld next week.

Talks are expected to center on Iraq, but the ministry said only that the two men would discuss "matters of mutual interest."

Duncan Smith, whose once-dominant party has struggled to gain ground against Labor, said Saddam must not be allowed to develop more weapons of mass destruction, including nuclear weapons.

"Ultimately, the question is not whether we deal with Saddam, but when and how," Duncan Smith said.