BRUSSELS - NATO is on track to start transferring control of parts of Afghanistan to the government's security forces -- a key element in the West's exit strategy from the decade-long war, the alliance's chief official said Friday.

The transition plan is due to be announced publicly by Afghan President Hamid Karzai on March 21. NATO and Karzai hope it will leave Afghan troops in control of the nation by the end of 2014, when international troops are scheduled to end their combat role.

The first phase of transferring control will probably begin in April or May, soon after Karzai's announcement.

NATO Secretary-General Anders Fogh Rasmussen said the Afghan army and police have made great progress and are increasingly joining the international forces on operations,

"They are now ready to gradually assume lead responsibility for the security of their nation and their people," he told NATO defense ministers, who are meeting to endorse the transition plan.

Officials and diplomats who spoke on condition of anonymity due to the sensitivity of the issue, said six areas -- including the provincial capitals of Lashkar Gah, Herat and Mazar-i-Sharif -- are slated to be handed over in the first phase.

All of Bamiyan and Panshir provinces, which have seen little to no fighting, are on the transition list. Also slated for transition is Kabul province except for the restive Surobi district.

A NATO spokesman in Brussels declined to comment on the list. Afghan Defense Minister Rahim Wardak said he expects alliance ministers to endorse the list of provinces and districts to be turned over to Afghan control.

Fogh Rasmussen said "we are putting great pressure on the insurgency, and are taking away many of the safe havens they relied on."

He was speaking at the start of a meeting of NATO's 28 defense ministers and their counterparts from 20 other nations participating in the international force in Afghanistan. Gen. David Petraeus, the top U.S. and NATO commander in Afghanistan, was due to brief the ministers about progress in the war.

There are 145,000 U.S. and NATO troops in Afghanistan. The Afghan government plans to have 305,000 soldiers and policemen by October. They face about 25,000 Taliban insurgents.

U.S. and NATO troops are due to start drawing down their forces in July. Fogh Rasmussen said the transition did not mean NATO would completely leave Afghanistan after 2014.

"On the contrary, our forces will remain in Afghanistan to support and train the Afghans," he said.