LONDON - British forces have entered the final stages of evacuating people from Kabul's airport and processing facilities have closed, Britain's defence ministry said on Friday.

The effort would now focus on evacuating British nationals and others who have already been cleared to leave and are already at the airport, the ministry said.

No further people would be called forward to the airport for evacuation, it said.

"It is with deep regret that not everyone has been able to be evacuated during this process," defence minister Ben Wallace said in a statement.

Wallace later told Sky News television that Thursday's attack at the airport, which killed 85 people including 13 U.S. soldiers, had not sped up Britain's timetable for ending the evacuation operation.

He said the threat of further attacks would grow as the operation neared its conclusion.

So far, Britain has evacuated more than 13,700 British nationals and Afghans, representing the second biggest airlift by the country's air force after the Berlin Airlift in 1949, the ministry said.

(Writing by William Schomberg and Kate Holton) ((; +44 207 542 7778; Reuters Messaging: