The United States is calling on Zimbabwe's neighbours to join international efforts to bring down President Robert Mugabe.
The US accuses Mr Mugabe of dragging the country into economic collapse and says he is responsible for a cholera outbreak that has killed more than 1000 people.
Reports suggest the Zimbabwe government is planning to counter the effects of international sanctions by nationalising industries like mining, banking and manufacturing.
The US has said that a power-sharing deal in Zimbabwe will not work with Mr Mugabe as president. It believes he has "reneged on that deal".
The American Assistant Secretary of State for African Affairs, Jendayi Frazer, has already urged Zimbabwe's neighbours to step up the pressure, saying they were protecting Mr Mugabe by failing to take a tougher diplomatic line.
Now State Department spokesperson Sean McCormack is also calling on South Africa and other neighbouring countries to act.