Sweden's Social Democrats and Greens, in negotiations to form a government, announced Wednesday they had reached an agreement to freeze nuclear energy development.

The deal was presented by incoming Social Democratic Prime Minister Stefan Loefven and Green Party spokeswoman Aasa Romson as a way for Sweden to eventually abandon nuclear power, but its details were not revealed.

No deadline was scrapping nuclear power was specified. The party leaders said it needed further discussion.

"The government's starting point is that nuclear power must be dismantled, we must have 100 percent renewable energy. But let us first have this analysis phase," Loefven told public broadcaster Sveriges Radio (SR).

The Green Party spokeswoman said there would be government subsidies for new nuclear power plants and that her party wanted to see several plants closed down within the next four years.

"We have clear security requirements that will be implemented, and as a consequence all energy experts say that old reactors will be closed down in the near future," Romson said.

According to SR, the agreement would not entail a premature closure of reactors, which was included in the Green Party's election manifesto.

The party is set to join a Swedish government coalition for the first time in its history.

Sweden has three nuclear plants with ten reactors, which were opened in the 1970s and 1980s. The oldest reactors are scheduled for closure in the 2020s.

The outgoing centre-right government, which lost the September general election and has been in power since 2006, was in favour of expanding the country's nuclear power capacity.

Despite a 1980 referendum where a majority voted to phase out nuclear power, the Swedish parliament passed a bill in 2010 to replace old reactors.