"I want to be clear: the EU is not prepared (for) lifting the restrictions we have on Zimbabwe," said Reinfeldt, whose country currently holds the rotating EU presidency.
"It is not the restrictions that are creating problems in Zimbabwe, it is the mismanagement … not respecting of human rights," he said in response to a question at a public address in Johannesburg.
Reinfeldt was speaking before a meeting with South African leader Jacob Zuma, whose government has come out strongly in support of the dropping of sanctions, ahead of a landmark EU visit to Zimbabwe at the weekend.
A high-level delegation will leave for Zimbabwe after a EU-South Africa summit Friday to work on normalising ties, the first such visit since sanctions were imposed in 2002.
Both the EU and the United States maintain a travel ban and asset freeze on President Robert Mugabe, his wife and inner circle in protest at controversial elections and alleged human rights abuses.
The 85-year-old leader appeared to score a diplomatic triumph on Tuesday when regional leaders made a call for the international community to remove all sanctions at a Southern African Development Community (SADC) summit.
Reinfeldt said Zimbabwe would be an "important part" of his meeting with Zuma in Cape Town later Thursday, following the resolution.
"I am interested to hear what President Zuma’s views are on the outcomes of the SADC summit. We depend on African leaders to be there and present, and to also influence," he said.
The EU visit follows the first official talks in seven years, held three months ago, with Prime Minister Morgan Tsvangirai who joined Mugabe in a unity pact nearly a year after chaotic polls pushed Zimbabwe deeper into crisis.
A unity government was formed in Zimbabwe in February and has acted to steer the country back to stability and restore the hyperinflation-ravaged economy and basic services that collapsed under Mugabe’s three decades of rule.
But the government has been plagued by power struggles over key posts and claims of continued persecution of Tsvangirai’s supporters, with Western states so far proving reluctant to give direct aid without proof of more reforms.
Swedish International Development Cooperation Minister Gunilla Carlsson and EU Aid Commissioner Karel De Gucht will meet Mugabe and Tsvangirai, as well as other ministers, officials and representatives of non-governmental organisations.
"This is a critical time for Zimbabwe and the weight of responsibility falls squarely on the country’s leaders to deliver urgent political, economic and social progress for the benefit of all the people of Zimbabwe," said de Gucht.
"There is an urgent need for all parties to fulfil their obligations," he said in a statement.
South Africa, which negotiated the unity pact, on Wednesday defended the regional call on sanctions, saying it was "a very responsible approach" to Zimbabwe’s troubles as it attempts to claw its way back from economic ruin.
"This call for the lifting of sanctions is not aimed at protecting and defending President Robert Mugabe as an individual. It is meant to attract necessary investments into Zimbabwe so that their economic recovery plan can take effect," said Deputy President Kgalema Motlanthe.