Britain has invited more than 60 nations, including foreign ministers from countries neighbouring Afghanistan such as Iran, to Thursday's talks on how to end the Afghan conflict.
"Because this meeting's approach is towards increasing military action in Afghanistan … and because it does not take into consideration the region's capacity to solve the problems, Iran does not consider as useful attending this meeting," Iranian Foreign Ministry spokesman Ramin Mehmanparast was quoted as saying by the semi-official Fars news agency.
Mehmanparast also criticised such meetings' lack of attention "to the root of problems" in Afghanistan.
Afghanistan's neighbours, including Iran, met in Istanbul on Tuesday to find a "single voice" in their approach to the conflict before the London conference.
Relations between Britain and Iran are strained over the Islamic Republic's disputed nuclear programme. The Iranians also accuse Britain of fomenting anti-government protests.
"Our expectation was that Iran would be represented. They were certainly invited and we were expecting a representative from Iran," said a spokeswoman for British Prime Minister Gordon Brown. "Clearly we are hoping that there will be representation, perhaps from their London embassy, but we'll see."
(Additional reporting by Adrian Croft in London)
(Editing by David Stamp)
