LONDON (AP) - The British government set out proposals yesterday to add a third runway and a sixth terminal at Heathrow, one of the world's busiest airports.

Transport Secretary Ruth Kelly said the expansion was needed to aid economic growth and that the expansion would meet tough environmental standards.

"Heathrow supports 170,000 jobs, billions of pounds of British exports and is our main gateway to the global economy. But for too long it has operated at nearly full capacity, with relatively minor problems causing severe delays to passengers," Ms. Kelly said.

"If nothing changes, Heathrow's status as a world-class airport will be gradually eroded - jobs will be lost and the economy will suffer," she added.

The public has until February 27 to comment on the expansion proposals, Kelly said.

The Competition Commission criticized British airports operator BAA last month for failing to manage long lines at Heathrow and causing "unacceptable delays to passengers, crew and flights."