The sanctions were originally imposed a decade ago in response to human rights abuses and political violence.

But sanctions would remain against President Robert Mugabe, AFP news agency quotes EU diplomats as saying.

"There is no question of lifting sanctions against Mugabe or anyone involved in continued abuses of human rights, incitement to violence," an EU official told the agency.

Mr Mugabe and his rival, Prime Minster Morgan Tsvangirai, have been sharing power since disputed elections marred by violence in 2008.

Fresh elections are expected to be held sometime next year, after the referendum on the new constitution.

"The EU agrees that a peaceful and credible constitutional referendum would represent an important milestone in the preparation of democratic elections that would justify a suspension of the majority of all EU targeted restrictive measures against individuals and entities," the EU foreign minister's statement said.

The BBC's Africa correspondent Andrew Harding says the new constitution should make it much harder for President Mugabe's supporters - or anyone else - to rig elections.

But there is still a great deal of concern that hardliners in Mr Mugabe's Zanu-PF party may try to derail the entire process, he says.

For years they have blamed Western sanctions for Zimbabwe's economic collapse; if those sanctions vanish - they lose one of their main rallying cries, our reporter says.