WASHINGTON, July 29 (AFP) -The United States reserves the right to respond to threats from Iraqi leader Saddam Hussein, national security advisor Condoleezza Rice told CNN's Late Edition on Sunday.

President George W. Bush "has made it very clear that he considers Saddam Hussein to be a threat ... (and) has reserved the right to respond when that threat becomes one that he wishes no longer to tolerate," she said.

However, she added, "I think it's always best not to speculate about the grounds or the circumstances under which one would do that."

House Minority Leader Democrat Dick Gephardt, speaking on the same program, agreed: "I fully back the administration in sending further messages to Saddam Hussein."

"We don't want our flyers at risk."

Their comments came even as Baghdad vowed Sunday to continue to resist US-British reconnaissance missions over Iraqi territory, just days after Iraqi forces tried to shoot down a U-2 spy plane.

Pentagon officials, while providing few details, have portrayed the incident as part of a continuing pattern of almost daily Iraqi attacks on coalition warplanes enforcing no fly zones over northern and southern Iraq.

Iraq does not recognize the zones and claims that 353 people have been killed and more than 1,000 injured in US and British attacks since December 1998, when they mounted heavy punitive air raids on Baghdad.

Rice also said the Bush administration was working with US allies to create a broad policy towards Iraq which would revisit efforts to impose narrower, tighter sanctions on Baghdad after backing away from a showdown with Russia in the UN Security Council on the issue.

"The administration is working hard with a number of friends and allies to have a policy that is broad. That does look at the sanctions as something that should be restructured so that we have smart sanctions that go after the regime, not after the Iraqi people," she said.

The US- and Britain-backed draft resolution brought to the council a month ago proposed scrapping the 11-year-old embargo on civilian trade with Iraq while tightening controls to prevent it from smuggling crude oil and illegal weapons.

Instead, the council voted unanimously to roll over the United Nation's humanitarian programme in Iraq for 150 days from midnight July 3.

"We in fact had four of the five, of the permanent five (security council members) go along with the sanctions. We'll work with the Russians, I'm sure that we'll come to some resolution there because it is important to restructure these sanctions to something that works."