Assistant Secretary for African Affairs Johnnie Carson said Washington would maintain its targeted sanctions until "sufficient progress in the area of democratisation" was seen.

"The US continues to maintain sanctions on Zimbabwe and will do so until we believe that substantial and irreversible progress has been made in the implementation of the comprehensive peace agreement," Carson said.

The US slapped sanctions against more than 50 government, military and ruling party officials in protest over controversial elections and alleged human rights abuses by Mugabe's government.

"We will continue to review our sanctions and we have taken a few people off the list, [but] not as many as the EU," he added.

Zimbabwe's two main political parties this week announced they had ironed out issues stalling the crafting of a new constitution that would pave the way for fresh polls.

Zimbabwe currently runs on a wobbly unity government between Mugabe and Movement for Democratic Change leader Morgan Tsvangirai formed three years ago to avoid an all-out conflict in the wake of a 2008 bloody presidential run-off election.

The EU has also kept a travel ban and asset freeze on Mugabe and his inner circle.