State Department spokesman Robert Wood questioned the pace of reform since February when veteran President Robert Mugabe formed a unity government with opposition leader Morgan Tsvangirai.

"These … 18 leading Zimbabwean activists ordered back to jail is troubling," Wood told reporters. "This is just another example of my concern about the lack of democracy, democratic processes in Zimbabwe," he added.

"We’ve got a lot of concerns about what’s going on there. And so, up until we see changes, our position is going to remain," he said, referring to any major U.S. aid kicking in.

The activists, who face charges of terrorism, were ordered back to prison by a Zimbabwean court in a move that will spark new tensions in a government formed after months of bickering and a crackdown by Mugabe’s forces on the opposition.

The activists say they were abducted by state security agents from their homes last year and tortured to force them to confess to planning to remove Mugabe from power.

The Obama administration has said repeatedly no significant aid can flow to Zimbabwe until the government has implemented a string of economic, political and democratic reforms.

Zimbabwe’s finance minister, an ally of Tsvangirai, met senior U.S. diplomats when he was in Washington at the end of last month to explain what reforms were planned. 

"Our position remains that we’re not going to be able to provide development assistance to the government of Zimbabwe until we see some steps toward power-sharing toward democratic reforms, economic reforms," Wood told reporters.

ECONOMIC CRISIS

Zimbabwe’s economy is in tatters with hyperinflation and unemployment at around 90 percent. The United States blames the decline on Mugabe’s mismanagement while the strong-arm African leader says Western sanctions caused the economic collapse.

The former Bush administration lost patience with Mugabe during negotiations to form the new government and then-Secretary of State Condoleezza Rice said it was time for the veteran African leader to go for the sake of his country.

Asked whether the Obama administration thought Mugabe should step aside, Wood said it was up to the Zimbabwean people to decide.

"We’ve, of course, you know, noted our concerns about Robert Mugabe and his policies and how this administration wants what’s best for the Zimbabwean people, and that’s for them to be able to determine their future in a democratic and transparent way, free from all this harassment and violence that’s been perpetrated upon them."