"The U.N. will either be able to function as a peacekeeping body as we head into the 21st century, or it will be irrelevant. And that's what we're about to find out," he said. "Make no mistake about it: If we have to deal with the problem, we'll deal with it."
Vice President Dick Cheney echoed Bush. "We'd prefer to do this on an international basis with the approval and cooperation and support of other nations," he said in a CNN interview. "This is deemed to be such an important issue and such an important problem that we will address [it] by ourselves if we have to."
Bush spoke alongside Italian Prime Minister Silvio Berlusconi, the second foreign leader in two weeks to visit Bush at Camp David for strategy sessions on Iraq.
Berlusconi, who has laid out a case for ousting the Iraqi president, has insisted that any action be taken with the United Nations' approval.
He joined Bush in warning that the United Nations' credibility was on the line. "The United Nations cannot continue to see its image undermined and its resolutions [flouted]," Berlusconi said through a translator.
Italy will play a key role in the campaign for approval through its ties to European Union countries and its "special friendship" with Russia, Berlusconi said.
Repeating the case he outlined to the U.N. General Assembly on Thursday, Bush said Hussein had "stiffed the world 16 times" by defying U.N. resolutions on his weapons programs.
Asked why Iraq deserved another chance to comply, Bush said the standoff is as much a test of the United Nations as it is of Hussein.
"This is the chance for the United Nations to show some backbone and resolve as we confront the true challenges of the 21st century," Bush said.
His administration is seeking a new U.N. resolution giving Iraq a firm deadline, just weeks away, to disarm or face dire consequences. Discussions at the United Nations continue this week on a range of issues, mainly about what to do if Hussein fails to comply.