BRUSSELS: EU nations agreed Thursday to slap sanctions on Iran's central bank, freezing assets potentially used to finance its nuclear programme, but have not yet clinched an oil embargo deal, EU diplomats said.

"The text was considered closed and agreed," a source said of the financial sanctions after talks between senior diplomats from the 27 EU nations to agree action against Iran, which is to be formally adopted by foreign ministers Monday.

The freeze on assets held by Tehran's central bank is to be partial, "enabling legitimate trade to go ahead" and ensuring payment of outstanding Iranian debts to Europe, an EU diplomat said.

But the diplomats were unable to clinch all details of an oil embargo, said the source, speaking on condition of anonymity.

"They'll have another go on Monday morning" ahead of the foreign ministers' meeting, "but it is likely that the oil embargo will have to go directly to the foreign affairs council" of ministers, said another diplomat.