President Bush said Saturday the U.S. was working on ways to punish Zimbabwe's longtime leader and his allies, branding Robert Mugabe's government as "illegitimate" and retaining power only through a "sham" election.

Bush instructed Secretary of State Condoleezza Rice and Treasury Secretary Henry Paulson to develop penalties against Mugabe's government in response to the widely denounced runoff election Friday. The African nation's president is accused of using violence to coerce people to vote for him.

Earlier Saturday, Rice said the U.S. plans to introduce a U.N. resolution as early as next week seeking tough measures against Zimbabwe.

"We will press for strong action by the United Nations, including an arms embargo on Zimbabwe and travel ban on regime officials," Bush said. He pledged to work closely with groups in Africa and world leaders to resolve the crisis.

Bush said the U.S. is ready to support a legitimate government with development aid, debt relief, and normalization with international financial institutions. The United States will continue to provide food assistance to more than 1 million people in Zimbabwe and AIDS treatment to more than 40,000 people.

"The Mugabe regime held a sham election that ignored the will of the people of Zimbabwe," Bush said in a statement issued while he spent the weekend at Camp David presidential retreat in Maryland.

"The international community has condemned the Mugabe regime's ruthless campaign of politically motivated violence and intimidation with a strong and unified voice that makes clear that yesterday's election was in no way free and fair," he said.

Bush said Mugabe was the leader of an "illegitimate government."

Rice told reporters traveling with her to South Korea that the U.S. and Britain could present a resolution to the Security Council as early as Monday. Rice declined to specify what it might say, but she said countries must act to halt further intimidation and violence against the Zimbabwe people.

"It is hard to imagine that anybody could fail to act given what we're all watching on the ground in Zimbabwe," she said.

"There needs to be a really strong message from the international community about what has happened there," she said.