European Union ambassadors agreed on Monday to impose an embargo on Iranian oil imports, but decided to delay the full implementation of the ban until July 1, an EU diplomat said.

Their agreement was the final step before EU foreign ministers can give their formal approval to the measure. The EU's 27 foreign ministers meet in Brussels on Monday.

(EU ambassadors) have agreed on Iran sanctions, the senior EU diplomat said, speaking on condition of anonymity.

Under the deal, EU governments will have to stop signing new contracts with Tehran from the moment the ban comes into place -- probably as soon as this week -- but will be able to fulfil existing contracts until July 1.

EU ministers are also expected to agree extra restrictive measures on Iran's central bank at Monday's meeting, but no details on those steps were immediately available.

(Reporting by Justyna Pawlak; editing by Luke Baker)