By Alastair Leithead
BBC News, Kabul
The Afghan government is expected to approve of Mr Eide
The new United Nations special envoy to Afghanistan, Kai Eide, has arrived in Kabul to take up his new post.
The former British politician Lord Paddy Ashdown was blocked from taking the job by President Hamid Karzai.
"I'm not Paddy Ashdown, but don't under-estimate me," Mr Eide said in remarks to the BBC.
He will attend a Nato summit in Bucharest next week which will be dominated by the international efforts in Afghanistan.
Mr Eide arrived at Kabul International Airport in a small United Nations plane from Dubai and made a brief statement.
He talked of bringing new direction and change to the international efforts in Afghanistan and made reference to a report released this week about the ineffectiveness of aid.
More money must be spent in the country on what the government wants, he told a news conference.
"One of the issues that has been highlighted is the need for better coordination," Mr Eide said. "The Afghan government has asked for that for a very long time and we have to respond in a better way than we have managed so far."
Mr Eide, a Norwegian diplomat, has been travelling to and from Kabul for the past five years.
The former British politician and High Representative in Bosnia, Lord Paddy Ashdown, was initially lined up for the UN special representative job, but his appointment was blocked by President Karzai in January.
Mr Eide is holding a series of meetings in Kabul over the coming days, including an audience with President Karzai.