Zimbabwe says it is not inviting Western observers to the constitutional referendum and elections due this year.
Foreign Minister Simbarashe Mumbengegwi told the state-owned Herald newspaper that EU and US observers lacked objectivity.
Zimbabwe is due to hold a referendum on 16 March on a constitution that will limit presidential powers.
It will be followed by elections, ending the coalition between Mr Mugabe and his rival, Morgan Tsvangirai.
'Up in smoke'
The two, aged 89 and 60 respectively, will run against each other in the election, after reaching a deal over a constitution that they have urged voters to endorse in the referendum.
Mr Mumbengegwi said Western observers would not be welcome because of sanctions the European Union (EU) and US had imposed on Mr Mugabe and other top officials from his Zanu-PF party over alleged human rights abuses.
"To be an observer, you have to be objective and once you impose sanctions on one party, your objectivity goes up in smoke," Mr Mumbengegwi, a Zanu-PF member, is quoted as saying.
"I do not see why they need to be invited when they have never invited us to monitor theirs."
Mr Mumbengegwi said Zimbabwe had already invited observers from the African Union (AU) and two regional bodies, the Southern African Development Community (Sadc) and the Common Market for Eastern and Southern Africa (Comesa), to monitor the referendum.
The EU and US imposed sanctions on Mr Mugabe and his inner circle after accusing them of unleashing violence and rigging previous election to prevent Mr Tsvangirai and his Movement for Democratic Change (MDC) from taking power.
The conflict ended after Zanu-PF and the MDC agreed to form a coalition government under pressure from regional leaders.
Under the new constitution, the president who wins this year's election, expected to be held in July, will be able to serve a maximum of two terms.
Mr Mugabe has been in power since independence in 1980.
Last month, Deputy Justice Minister Obert Gutu said there had been an arson attack on the home of MDC activist Shepherd Maisiri in the eastern farming district of Headlands, causing the death of his 12-year-old son, Christpower.
Mr Gutu, an MDC member, blamed supporters of Zanu-PF for the attack and said it did not bode well for a peaceful referendum and election.
A Zanu-PF spokesman said the attack was an attempt to discredit his party.