The cost of buying one advert during the final episode of Friends in the US will be $2m (£1.24m), making the commercial breaks the most expensive ever for a non-sports programme.

Friends broadcaster NBC is asking advertisers for the kind of money usually reserved for the biggest event in the US broadcasting calendar, the Super Bowl, according to US media buyers.

More than 100 million viewers tune in to the Super Bowl and reaching that colossal TV audience costs advertisers up to $3m (£1.9m) for a 30-second ad.

The two-hour finale to the 10th and final series of Friends will be one of the most hyped entertainment programmes in TV history and NBC is setting its ad rates accordingly.

A 30-second spot in Friends sells for about $450,000 (£280,000) and the show usually attracts 20 million viewers.

The decision to extend the length of the final show to two hours is unprecedented for a 30-minute programme.

In May 1998, when Seinfeld - then America's most popular TV comedy - reached the end of its run, the hour-long finale was a national event attracting more than 80 million viewers.

The end of Friends, which inherited Seinfeld's crown as the top US sitcom, is likely to pull in a similar audience.

The NBC entertainment chief, Jeff Zucker, outlined the network's plans for Friends at a presentation for ad buyers in New York this week.

Mr Zucker said NBC will ask viewers to vote for their six favourite episodes and will broadcast them in the weeks leading up to the finale next May.

Jennifer Aniston and the five other stars are being paid $1m (£700,000) for each of the 18 episodes in the final series.