Anheuser-Busch InBev, the brewery behind Budweiser, is to cut 1,400 jobs in the US - 6% of its American workforce - to help it save $1.5bn (£1bn) a year.

Three-quarters of the cuts will be made at Anheuser's headquarters in St Louis, and will go beyond plans that the company announced this summer to streamline costs before it agreed to a takeover by Belgium-based brewer InBev. The firm said the job losses will help it cope with a "challenging economy." Most of the cuts will happen by the end of the year.

Anheuser-Busch provides half of the beer drunk in the US, but the company has not managed to expand globally as fast as the Belgian-Brazilian hybrid InBev, which owns hundreds of local brands but few big names. Beer sales in both the US and Europe are slowly declining.

InBev wrapped up its $52bn takeover of Anheuser-Busch last month. Anheuser had 8,600 salaried workers this summer, and had planned to reduce that by 10-15%, mostly by offering 1,000 employees voluntary early retirement. That plan was meant to save the brewer $1bn a year.

The latest cuts mean the brewer will lose a quarter of the workers it had at the start of 2008. More than 250 unfilled jobs will be cut, along with 415 contractor positions. Around a quarter of job cuts will be in field and brewery locations, it said.

"To keep the business strong and competitive, this is a necessary but difficult move for the company," said Anheuser-Busch president David A Peacock.

Workers who form part of a trade union at the company's 12 North American breweries will not be affected. InBev pledged not to close any of the breweries as long as it was not forced to pay any extra taxes.

The redundancies will cost the company $197m, mostly in severance payments and pension benefits.

InBev is known for tight cost control since its formation in a 2004 merger between Brazil's AmBev and Belgium's Interbrew. The Brazilian management team who headed the company had a sharp focus on costs which was said to have come as a shock to the European business