World powers will fail to reach a consensus on imposing new sanctions against Iran over its controversial nuclear program, the foreign ministry said Sunday. Ministry spokesman Ramin Mehmanparast told the official IRNA news agency that the P5+1 group, comprising the United States, Britain, France, Russia, China – five veto-wielding members of the UN Security Council - and Germany, would not succeed in imposing sanctions on Tehran. “Since the principle of sanctions regarding Iran's peaceful nuclear activity lacks a logical and legal basis and is being pursued with political intentions by some countries, it is natural that sanctions will not materialize,” Mehmanparast said. The United States has stepped up pressure to generate international backing for a fourth round of UN sanctions against Iran. Western governments are losing patience with Iran for rejecting a UN-brokered nuclear fuel deal and for enriching uranium – the most controversial part of Tehran's atomic program – to higher levels. While the US, France, Britain and Russia appear to favour sanctions, China, which has large oil interests in Iran, continues to strongly advocate diplomacy to resolve the crisis. A defiant Tehran insists its nuclear programme is for peaceful purposes and is already under three sets of UN sanctions for enriching uranium. Meanwhile, Tehran prosecutor Abbas Jafari Dolatabadi denied reports that a death sentence imposed on a student for taking part in anti-government protests has been upheld by an appeals court, ILNA news agency reported. Several opposition websites reported Wednesday that a death sentence issued by the court of first instance against Mohammad Amin Valian, 20, had been upheld by an appeals court. Dolatabadi denied these reports, saying Valian still had time to appeal against the verdict and indicated that the protester's case had not even reached the appeals court yet. “Mr Valian is like several others accused in Ashura incidents whose verdict has been issued (by the court of first instance)... and he has up to March 13 to appeal,” ILNA news agency quoted Dolatabadi as saying. “Some people have used this verdict to spread wrong news. The upholding of this verdict by the appeals court is denied.” Ahmadinejad heads to Kabul Iranian President Mahmoud Ahmadinejad is to make a one-day trip to neighboring Afghanistan Monday to discuss with his counterpart Hamid Karzai how to stabilize the war-torn nation, Iran's Mehr news agency reported. Mehr said the two men would “examine solutions to Afghanistan's problems” as Iran seeks to boost relations. Ahmadinejad has repeatedly called for the withdrawal of US-led forces from Afghanistan, saying their presence was stoking the Taliban insurgency.