Apparently the Iranians believe that they are already in a position to assert their power in Iraq. From AP, with thanks to Mackie:
BAGHDAD, Iraq (AP) — Iran’s foreign minister demanded the immediate withdrawal of British forces from Basra on Friday, saying their presence had destabilized Iraq’s second-largest city.
British Prime Minister Tony Blair rejected the demand and accused Iran of trying to divert attention from other issues, presumably its nuclear program. A Basra city spokesman said the departure of foreign troops “is not in Iraq’s interest now” because of the security situation.
“We believe that the presence of British forces in Basra has destabilized security in this city and has had some negative effects in the form of threats against southern Iran recently,” Foreign Minister Manushehr Mottaki said during a visit to Beirut, Lebanon.
“The Islamic Republic of Iran demands an immediate withdrawal of British forces from Basra,” he added. Basra, where most of Britain’s more than 8,000 troops in Iraq are based, is located about 20 miles west of the Iranian border.