The United States' outgoing ambassador to Zimbabwe said Tuesday that Washington would only lift sanctions against President Robert Mugabe and his inner circle if polls are held peacefully.
"There are disturbing signs of potential violence," Charles Ray said in a farewell address to journalists on completing his tour of duty in Harare.
"There have been disturbing reports recently that could be problematic in an election environment."
The ambassador's remarks came a day after the European Union agreed to lift most sanctions imposed on Mugabe's inner circle if the country holds a "credible" vote on a new constitution.
Ray said the United States would only lift its own sanctions on Mugabe and his close associates after Washington is satisfied with the electoral conditions in Zimbabwe.
"Sanctions were a response to a violent electoral process," he said. "A credible electoral process free of violence and intimidation would make our current policies irrelevant. The ball is entirely in this court.
"It's hard to say to my government they should do away with a policy that we put in place as a response to certain issues when those issues have not been adequately addressed."
Sporadic cases of violence have been reported across Zimbabwe in recent months including the murder of a district official from Prime Minister Morgan Tsvangirai's party by Mugabe supporters.
Mugabe and Tsvangirai were forced into a coalition government three years ago to avoid a tip into fully-fledged conflict following a bloody presidential run-off election.
A local daily last week reported an incident in which soldiers teamed up with youth from Mugabe's party to block a rally that was to be addressed by Finance Minister Tendai Biti, a Tsvangirai ally.
The ambassador, who is retiring after 50 years in the military and diplomatic service, also urged security chiefs to keep out of politics.
"The role of the military is to defend the nation," Ray said.
"In order to do that they must develop a degree of professionalism. It means that military people, in order to remain professional and of service to the country, must delink their personal political convictions from the carrying out of their professional duties."
Some security chiefs have been quoted in the media making partisan political statements including suggestions that they would only recognise a leader with credentials from the country's 1970s liberation war.