What should the U.S. do about Zimbabwe?

Are the sanctions to be imposed by the G-8 nations on Robert Mugabe and his inner circle a sufficient response by the U.S. to the situation in Zimbabwe? Should the U.S. and it's allies do more to attempt to oust Mugabe and end the suffering of his opponents?

Clearly, the recent "election" in Zimbabwe was a sham, the continued rule of Mugabe is illegitimate and the country's economy is on the brink of total collapse. The U.S. and Britain were correct to make Zimbabwe a major issue at the G-8 conference in Toyako. They are also right to keep pushing sanctions (and appropriate relief) at the U.N. level. But suppose the U.N. decides not to get involved? I believe that with their relative wealth, both the U.S. and Britain, along with other G-8 nations, would then have a moral responsibility to provide assistance to affiliates of opposition leader Morgan Tsvangirai and his Movement for Democratic Change (MDC), not only in the form of humanitarian aid but also strategic aid.