The United States Thursday expressed deep concern about the cholera outbreak in Zimbabwe that prompted the Harare government to declare a national emergency. U.S. aid officials are considering a response.

Officials here said the U.S. Agency for International Development is looking into what can be done to help deal with the health crisis in Zimbabwe. But they said the United States' ability to respond is limited by the troubled political situation in that country.

Zimbabwe's health ministry Thursday declared a national emergency amid a cholera outbreak complicated by an economic crisis that has closed many of the country's main hospitals and rural health clinics.

The British government has said it intends to boost humanitarian aid to Zimbabwe despite its conflict with the government of President Robert Mugabe.

At a news briefing, State Department Deputy Spokesman Robert Wood said the United States is very concerned about the health - as well as the political and economic -- situation in Zimbabwe and that the aid agency "is taking a strong interest" in what can be done.

But he said it is the responsibility of Mr. Mugabe to cooperate with the international community in trying to deal with those issues, including the country's ongoing political crisis.

"It's really going to be incumbent on the Mugabe regime to first and foremost sit down with the opposition and work out some kind of political arrangement that represents the will of the Zimbabwean people, and then allow the international community to provide the type of assistance that's necessary. But it's a very difficult situation in Zimbabwe. We're obviously very, very concerned about the reports of these cholera deaths," Wood said.

The cholera outbreak, which the United Nations said has claimed nearly 600 lives, comes as Zimbabwe is crippled by an economic meltdown and political stalemate.

The government has been paralyzed for months amid stalled power-sharing talks between Mr. Mugabe's ZANU-PF party and the opposition Movement for Democratic Change, which won parliamentary elections last March.

The United States and European allies have stepped up sanctions targeted against Mr. Mugabe and key associates to try to pressure him to share power. The long-time leader blames the country's problems on Western sanctions.

A senior U.S. diplomat who spoke to reporters said the United States wants to help the Zimbabwean people in the latest crisis but that the Harare government "has not been forthcoming" in terms of accepting outside aid.

The official accused Mr. Mugabe of "destroying" the country's economy and said he just does not seem to want to negotiate fairly and objectively with the opposition.

British Prime Minister Gordon Brown said Thursday that Mr. Mugabe's "failed state" is no longer willing or capable of protecting its people, and that the thousands stricken with cholera must be helped urgently.

Despite its targeted sanctions, the Bush administration has continued a $200 million a year humanitarian aid program for Zimbabwe.