Paddy Ashdown, the international community's former envoy to Bosnia, should not be the UN's new representative in Afghanistan, the country's ambassador to the world body has told the BBC.
In an interview published on the broadcaster's Web site late on Saturday, Zahir Tanin confirmed a newspaper report that Afghan President Hamid Karzai wanted to block Ashdown's appointment.
The Times quoted unnamed diplomats as saying on Saturday that Karzai thought Ashdown wanted too much power and had raised his objection with British Prime Minister Gordon Brown and US Secretary of State Condoleezza Rice last week.
Tanin told the BBC that the Kabul government's preferred choice instead would be NATO's deputy commander in Europe, General John McColl.
McColl was the first head of the international security force in Afghanistan in 2002 after the ouster of the hardline Taliban.
Tanin said government officials had been surprised to see Ashdown portrayed in the media as the final choice for the post when no formal announcement had been made.
"A negative atmosphere was generated through the media inside and outside Afghanistan, particularly in Britain, which hit a lot of nerves and paved the way for misunderstanding and concerns," he was quoted as saying.
Their preference for McColl was based on "who is going to be more helpful and who is going to be more able to work with the Afghan government and with different elements of the international community in Afghanistan", he said.
Ashdown, a former leader of Britain's second opposition party the Liberal Democrats, has declined to comment on reports of his appointment.
The ex-marine gained a reputation as a no-nonsense operator during his time in Bosnia from 2002 to 2005, pushing through sensitive reforms and sacking 60 officials suspected of belonging to a support network for war crimes suspects.
Karzai's opposition comes at a time of tension between Kabul and London.
At the World Economic Forum in Davos, Switzerland, last week, he was reported as having blamed British and US troops for contributing to worsening security in southern Afghanistan that had allowed the Taliban to return.
That prompted outrage from relatives of some of the 87 British service personnel who have died since the start of combat operations in Afghanistan in late 2001.