* Ban asked to tell Britain to stop "unilateral acts"
* British envoy says oil drilling quite legal
UNITED NATIONS, Feb 24 (Reuters) - Argentina asked the United Nations on Wednesday to step into its dispute with Britain over the Falkland Islands but U.N. officials said mediation would need the agreement of London.
Argentine Foreign Minister Jorge Taiana put the request to U.N. Secretary-General Ban Ki-moon two days after the long-running dispute erupted again when a British company began oil exploration off the South Atlantic islands, which Argentina calls the Malvinas.
Argentina, which has claimed the islands since Britain established its rule in the 19th century, invaded them in 1982. After a two-month war, it was forced to withdraw, but still claims the archipelago and says oil drilling by Britain's Desire Petroleum DES.L is a breach of sovereignty.
"We asked the secretary-general, in the exercise of his good offices, to transmit to the United Kingdom the need not to commit any more unilateral acts," Taiana told reporters after meeting Ban.
He said Britain should also comply with U.N. resolutions on "the need to sit down and negotiate with Argentina on the Malvinas conflict."
Britain has rejected Argentine objections to the oil exploration, saying the drilling is within international law.
"British sovereignty in respect of the Falklands is absolutely clear in international law," Foreign Secretary David Miliband said on Tuesday.
A U.N. General Assembly resolution entrusted the secretary-general months after the Falklands war with a "good offices" mission to try to resolve the sovereignty dispute.
A U.N. spokesman, Ari Gaitanis, said Ban "took note of Argentina's concerns" at the meeting with Taiana and welcomed Buenos Aires' commitment to resolve the dispute peacefully.
He did not say whether Ban would pass on Taiana's message to Britain but said the U.N. chief "reiterated that his good offices are available when requested by all parties in a dispute."
The phrase appeared to be a discreet recognition that Britain does not acknowledge that a sovereignty dispute exists and sees no case for mediation.
Referring to the specific issue of the oil exploration, however, British Prime Minister Gordon Brown said last week that "sensible discussions will prevail on this."
Reaffirming the British position after Taiana's meeting with Ban, Britain's U.N. Ambassador Mark Lyall Grant said his country "has no doubt about its sovereignty over the Falkland Islands ... This position is underpinned by the principle of self-determination as set out in the U.N. Charter."
"We are also clear that the Falkland Islands government is entitled to develop a hydrocarbons industry within its waters, and we support this legitimate business in Falklands' territory," Lyall Grant said in a statement.
Argentina has formally objected to the oil drilling near the islands and said it will require all ships from the Falklands to obtain permits to dock in Argentina.
The "Rio Group" of Latin American leaders, meeting this week in Mexico, issued a statement on Tuesday supporting Argentina's demands to halt drilling around the Falklands.
The Falklands are not an onshore oil producer and have no proven onshore reserves, but oil companies are betting that offshore fields hold billions of recoverable barrels of oil. (Editing by Cynthia Osterman)