U.S. president-elect Barack Obama should resist calls to change strategy in Afghanistan and focus on implementing the one already being pursued, says the UN's top official in Afghanistan.

The incoming U.S. administration "has a unique opportunity to gather strength, gather energy ... and build on the trends we have seen" toward building the Afghan security forces and propping up the country's economy, Kai Eide, head of the United Nations Assistance Mission in Afghanistan, told the Associated Press.

"My appeal is not grand strategy discussion, my appeal is concrete implementation effort," Eide said in an interview in Kabul on Thursday.

Obama has pledged to withdraw American troops from Iraq and deploy more to Afghanistan, where Taliban and al-Qaeda linked militants have made a comeback in recent years.

U.S. vice-president-elect Joe Biden, who toured the region earlier this month, said that "things are going to get tougher in Afghanistan before they're going to get better."

Insurgent attacks in Afghanistan increased in 2008 over the previous year and some 6,400 people — mostly militants — died last year as a result of the insurgency.

30,000 more U.S. troops to be sent

The deteriorating situation in Afghanistan has forced the U.S. to plan to rush as many as 30,000 more troops to the central Asian country this year.

They will be joining some 32,000 U.S. troops already there who serve alongside 32,000 other NATO-led and coalition troops — the highest number since the U.S.-led invasion that ousted the Taliban from power in 2001.

Obama has said Afghanistan is one of his top priorities, but his incoming team have not yet disclosed a concrete plan.

Eide, the Norwegian diplomat who has been heading the UN mission in Afghanistan for the last nine months, warned against any major change in direction.

"Our problem is not that we need a new strategy.... What happens very often is that we agree on something, we do not implement it and we say something must therefore be wrong with the strategy," Eide said. "That is not the case. The problem is in the implementation."

Eide said there have been major improvements in two important sectors — building of local security forces and the economy.

"Every month we are getting better at handling the security situation," he said. "There is a greater momentum in building the key parts of the economy."

Staying the course and implementing the priorities set up at an international conference over six months ago must remain the goal, Eide said.