Hitoshi Tanaka, deputy minister for foreign affairs, will head the Japanese delegation to the meeting, which will begin on Saturday, the foreign ministry said.

Negotiations over Japanese-Iranian joint development of the massive Azadegan oil field, situated in the southwest of the Islamic republic, are expected to figure high on the agenda.

"The Azadegan oilfield is one of the topics we are to discuss," a foreign ministry official said.

Japan and Iran agreed in 2000 to start negotiations over the field but Iranian officials warned that a period of exclusive signing privileges for the Japanese consortium expired at the end of June and other companies could now be considered.

The Azadegan field is considered to be the country's most important with estimated reserves of 26 billion barrels of oil.

Washington has been trying to persuade Japan to drop its investment due to concerns over Tehran's nuclear programme,

Asked if the United States had put fresh pressure on Japan to suspend negotiations, the official only said: "We are cordinating in this and other issues with the United States."

WAR.WIRE