The US envoy for Africa has threatened Zimbabwe with UN sanctions if the post-election crisis in the southern African nation is not resolved.
If the dispute does not change "we should contemplate multilateral sanctions through the UN," Jendayi Frazer, the US assistant secretary of state told BBC.
The UN Security Council will discuss the Zimbabwe crisis on Tuesday, with permanent members Britain and the United States ratcheting up the pressure on Robert Mugabe, the Zimbabwean president, who has ruled for 28 years.
Frazer earlier called for an end to the violence in Zimbabwe and said opposition leader Morgan Tsvangirai should head any new government, dismissing the prospect of a second round of the presidential election.
Results from the March 29 presidential election have still not been released but officials have said no candidate won more than 50 per cent and there should be a run-off between Tsvangirai and Mugabe.
Frazer has been on a tour of the region, which began in South Africa, to put pressure on Mugabe to step down. She has met with South African officials and the presidents of Angola and Zambia.