The United States urged the international community to keep up pressure on Zimbabwean President Robert Mugabe to implement a power-sharing agreement as friction mounted in his cabinet.

"We understand the frustration of the opposition in the lack of progress," State Department spokesperson Ian Kelly told reporters hours after Zimbabwean Prime Minister Morgan Tsvangirai suspended cooperation with Mugabe.

Tsvangirai's snub of what he termed Mugabe's "dishonest and unreliable" camp was sparked by this week's renewed detention of top aide Roy Bennett, whose release on bail was ordered by Zimbabwe's high court on Friday.

Bennett, who was Tsvangirai's pick as deputy agriculture minister but was arrested an hour before Mugabe swore in the new government in February, goes on trial Monday on charges the Movement for Democratic Change (MDC) says have been trumped up.

"Everybody needs to continue to put pressure on Mr Mugabe to implement the agreement" that set out the fragile new unity government, Kelly said.

"This is an agreement that Mr Mugabe himself signed, and he hasn't taken the concrete steps to show a commitment to democratic reform and opening up his political system."

Another State Department spokesman, Robert Wood, demanded Thursday that Mugabe "end the harassment of the opposition."