TEHRAN, Iran (AP) -- Iran has halted oil shipments to Britain and France, the Oil Ministry said Sunday, in an apparent pre-emptive blow against the European Union after the bloc imposed sanctions on Iran's crucial fuel exports.

The EU imposed tough sanctions against Iran last month, which included a freeze of the country's central bank assets and an oil embargo set to begin in July. Iran's Oil Minister Rostam Qassemi had warned earlier this month that Tehran could cut off oil exports to ``hostile'' European nations. The 27-nation EU accounts for about 18 percent of Iran's oil exports.

However, the Iranian action was not likely to have any significant direct impact on European supplies because both Britain and France had already moved last year to sharply curtail oil purchases from Tehran to less than 3 percent of their daily needs.

The EU sanctions, along with other punitive measures imposed by the U.S., are part of Western efforts to derail Iran's disputed nuclear program, which the West fears is aimed at developing atomic weapons. Iran denies the charges, and says its program is for peaceful purposes.

The spokesman for Iran's Oil Ministry, Ali Reza Nikzad-Rahbar, said on the ministry's website Sunday that ``crude oil exports to British and French companies have been halted.''

``We have our own customers and have no problem to sell and export our crude oil to new customers,'' he said.

Britain's Foreign Office declined comment, and there was no immediate response from French officials.

The semiofficial Mehr news agency said exports were suspended to the two countries Sunday. It also said the National Iranian Oil Company has sent letters to some European refineries with an ultimatum to either sign long-term contracts of two to five years or be cut off.

Mehr did not specify which countries were sent the ultimatum, but Spain, Italy and Greece are among Europe's biggest buyers of Iranian oil.

Iran's targeting of Britain and France appeared to be a political decision to punish the two countries for supporting tougher sanctions against Iran over its nuclear program.

Sunday's announcement follows a flurry of contradictory signals by Iran about backlash against the EU for imposing a boycott on Iranian oil.

Last week, state media said Iran was planning to cut off oil exports to six EU nations, including France, but later reports said the nations were only told that Iran has no problem finding replacement customers for the European shipments.

The EU sanctions, imposed last month, were part of Western efforts to target Iran's critical oil sector in attempts to rein in Tehran's nuclear program.

Also on Sunday , the secretary general of Iran's central bank said a decision by SWIFT, an international banking clearinghouse used by nearly every country and major corporation in the world, to shut Iran out from its respected network will not harm the country.

``The country will not face any problems as a result of the SWIFT measures,'' Mahmoud Ahmadi was quoted as saying by the official IRNA news agency. He added that Iran has been ``pursuing alternative solutions'' since Western nations imposed sanctions on Tehran. He did not elaborate.

SWIFT said in a statement on its web site Friday that it will comply with expected instructions from the EU to cut off Iranian banks. SWIFT has previously brushed off international efforts to use its network to target countries or companies, telling enforcers that it does not judge the merits of the transactions passing through the portal.