The United States has announced it is imposing economic sanctions on President Robert Mugabe and 76 other government officials in Zimbabwe.
Mugabe's policies constitute a "threat to the foreign policy of the US"
Washington accuses them of undermining democracy and using violence to stifle political opposition.
The executive order signed by US President George W Bush freezes the assets of those involved, and bars Americans from having any financial dealings with them.
The US sanctions mark an escalation of the visa restrictions on officials announced by President Bush last March following Mr Mugabe's controversial re-election last year.
A senior Zimbabwean official told Reuters news agency on Saturday that the move was part of what he called a "white racist" attack on Mr Mugabe's government.
The main opposition party in Zimbabwe, the Movement for Democratic Change, welcomed the American decision, but the South African Government reacted by saying it had never believed in sanctions.
America's actions complement a similar move by the European Union to freeze the assets of the leadership, the White House said.
The EU renewed its year-old sanctions - including travel restrictions on the country's leaders, an arms embargo and a freeze of assets - against Mr Mugabe and 71 of his associates in mid-February.
The government has systematically undermined democratic institutions, employing violence, intimidation, and repressive means to stifle opposition
On Tuesday, the US condemned the mass arrests of opposition supporters and various leaders in Zimbabwe and
called on other countries to join in its "forthright" condemnation of Harare.
Last month, Mr Mugabe launched a blistering attack on Mr Bush and UK Prime Minister Tony Blair, branding them imperialists who wanted to impose a new
form of colonialism on developing countries.
President Bush said in the order: "Mugabe's policies constitute an unusual and extraordinary threat to the foreign policy of the United States, and I hereby declare a
national emergency to deal with that threat."
The order "blocks all property and economic assets of the targeted individuals. It also prohibits US citizens or residents from engaging in any transaction or dealing
with the targeted individuals," White House spokesman Ari Fleischer said in a statement.
The move "makes clear our agreement that the situation in Zimbabwe endangers the southern African region and threatens to
undermine efforts to foster good governance and respect for the rule
of law throughout the continent," Mr Fleischer added.
"This action is aimed not at the people of Zimbabwe, but rather at those most responsible for their current plight. The US is acutely aware of the hardships and frustrations which the
Zimbabwean people are enduring."
The US will also try to ensure that adequate food supplies are made available to those in need, he said.