European Union leaders are concerned about the "expansion" of Iran's nuclear programme and its "possible military dimensions," according to draft conclusions of an EU summit on Sunday.

The EU leaders will denounce "unacceptable human rights violations" and voice their satisfaction over EU sanctions imposed on five Iranians over an alleged failed bid to assassinate the Saudi ambassador in the United States, according to the text.

The council of 27 EU states "urges Iran to respect all obligations under international law," says the draft text which is due to be adopted at the end of the day-long summit.

"It expresses its continued concern over the expansion of Iran's nuclear and missile programmes, in violation of UNSC (UN Security Council) and IAEA (International Atomic Energy Agency)" demands, it says.

The EU leaders also lament Iran's "lack of cooperation with the IAEA in addressing outstanding issues, including those pointing to possible military dimensions to its nuclear programme."

Western powers have imposed a raft of sanctions against Iran since 2007 over fears that the Islamic republic is seeking to build a nuclear bomb under cover of a civilian atomic programme. Tehran denies the charge.

The EU leaders reiterated the "commitment of the European Union to work for a diplomatic solution of this issue."