The European Union confirmed Monday that a ban on oil imports from Iran will go ahead as planned on July 1 due to the lack of progress in talks on Tehran's contested nuclear drive.

"The latest package of EU sanctions against Iran will apply as earlier decided," EU foreign ministers said in a statement.

Confirmation the embargo will be enforced comes days after talks flopped in Moscow between Iran and the P5+1 group (the United States, Britain, France, Russia, China and Germany). It was the latest of three high-level meetings in three months to fail to make headway.

"We've confirmed the details of the sanctions being imposed on Iran," said British Foreign Secretary William Hague.

"It is important that the Iranian leaders understand the resolve of the international community on this and that we will go on intensifying the economic pressure."

The West suspects Iran of seeking to make nuclear weapons under the guise of an energy programme and wants it to stop enriching uranium to 20 percent, which brings it dangerously close to levels needed to make a nuclear bomb.

Monday's statement confirmed a January 23 agreement by the 27-nation bloc to immediately ban new oil imports from Iran and phase out existing contracts by July 1.

The statement said that contracts for importing Iranian oil that were concluded before January 23 "will have to be terminated by July 1.

"From the same date, EU insurers may no more provide third-party liability and environmental liability insurance for the transport of Iranian oil," it added.

It said that "the objective of the EU remains to achieve a comprehensive, long-term settlement on the basis of meaningful negotiations" between world powers and Iran.

But EU foreign policy chief Catherine Ashton acknowledged "a very substantial gap currently exists between the two sides."

"We have real concerns," she told a news conference. "The sanctions are there to make the regime in Iran understand to take those concerns seriously and address them.

"We need to keep that pressure up."

Iran and the world powers are keeping the diplomatic track alive by agreeing to more discussions -- but at a lower level, between experts, to be held July 3 in Istanbul.

More senior-ranking discussions will only follow if those experts manage to drag the talks out of the impasse seen in recent months in Istanbul, Baghdad and Moscow.