Democratic presidential hopeful Hillary Rodham Clinton said President George W. Bush has made a mistake in failing to push direct diplomacy with Iran despite the increasing tensions between Washington and Tehran.

Asked at a campaign appearance Saturday what the United States should do in the event Iran blockades Mideast oil, the New York senator said, "I will make it very clear to the Iranians that there are very serious consequences attached to their actions."

Speaking at a town hall meeting with some 300 people at a high school in South Carolina, she said such consequences would be in the realm of sanctions. Clinton again defended her vote in the U.S. Senate for a resolution labeling Iran's Revolutionary Guard as a terrorist force, disputing critics who said her vote presaged support for war.

Clinton said the vote was consistent with her negotiating strategy. "They are supporting sending weapons into Iraq right now that are used against our troops," she said, adding that the resolution gives an opening to future penalties and "leverage when we negotiate with them."

Responding to a woman's question about such a hypothetical Iranian blockade, Clinton said it would be "devastating to the world economy."

She said she would "immediately open diplomatic negotiations with Iran over all of the issues we disagree with them on," and said she thought such talks would be indispensable to American credibility in the region, particularly if tougher actions had to follow.

"And I think that President Bush has made an error in not having that process, in not having our diplomats being in constant contact and negotiation," she said.

In another development, Clinton on Saturday won the endorsement of the black wing of the Alabama Democratic Party by capitalizing on long friendships that her Democratic rival Senator Barack Obama could not match. The Alabama Democratic Conference endorsed Clinton by an overwhelming voice vote moments after she addressed the audience of some 700. No other candidate was nominated for an endorsement.

An ADC member, Madison County Commissioner Bob Harrison said that Obama was the sentimental favorite for him and many others, but Clinton was the practical choice.

"This is the political reality of what the outcome is going to be for the Democratic nomination," he said.

On Friday, she was endorsed by Democratic Rep. John Lewis, one of the leaders of the Martin Luther King Jr. civil rights movement.

New Mexico Governor Bill Richardson, another Democratic presidential hopeful, said Clinton is "acting as if she's won" the nomination.

"I think this is a time when voters start making up their minds and we draw contrasts," Richardson told reporters Saturday after addressing a union picnic in Las Vegas. "This race is not over. ... We've got three months to go."