Iran's Economy Minister has warned that any international efforts to punish his country for resuming nuclear fuel research may lead to higher oil prices. Sanctions could upset "Iran's political and economic situation" leading to oil prices "beyond levels the West expects", Davoud Danesh-Jafari said. Iran denies it plans to develop nuclear weapons but has said it will not be intimidated by international pressure. The country is the world's fourth largest exporter of crude oil. Concerns over Iran and continuing unrest in Nigeria pushed up crude oil prices on Monday. Brent crude for March delivery rose 65 cents to $63.25 a barrel in London although the impact was limited by the closure of US markets for a public holiday. Mr Danesh-Jafari's comments on Iranian state radio came as the five permanent members of the United Nations Security Council and Germany met in London to discuss Iran's move to resume its nuclear fuel research. The US, Britain, France, Russia, China and Germany intend to discuss their strategy - including the possibility of sanctions - following the resumption of Iranian nuclear research. President George Bush has also refused to rule out military force - a view backed by politicians from both main parties in the US. World oil prices rose above $64 a barrel last week as hopes of a diplomatic solution to the growing international stand-off with Iran began to fade.