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German carmaker Volkswagen has posted its first drop in VW brand sales in 11 years as the company continues to cope with its emissions scandal.

Sales of VW brand cars fell 4.8% in 2015 to 5.82 million cars from 6.12 million a year earlier.

Falling demand in China and US added to the losses as orders fell in December.

VW has promised it will have a fix in the coming weeks for the millions of US cars with defeat devices that disguised emission levels in diesel cars.

Sales began declining after the scandal came to light in September. Deliveries fell 5.3% in October, 2.4% in November and 7.9% in December compared with those months the previous year.

The underperformance at VW's largest division by sales and revenue pulled down annual group deliveries by 2% to 9.93 million cars, the first drop in 13 years, VW said.

However, speaking on Wednesday, Volkswagen chief executive Herbert Diess said he was "optimistic" the company would find a solution soon.

"We will bring a package together which satisfies our customers first and foremost and then also the regulators," said Mr Diess.

Regulators appear been less confident. The Environmental Protection Agency (EPA) which uncovered the scandal, said on Monday that VW had not yet "not produced an acceptable way forward".

The company will meet US regulators in Washington next week to discuss its plan.

US charges

On Monday, the US Justice Department filed a lawsuit against VW for the use of the emissions devices, which involve computer software that can detect when cars are being tested.

The Connecticut Attorney General George Jepsen said on Friday that the company was not cooperating with the investigation.

Volkswagen has been withholding corporate emails between executive related to the emissions scandal, using German law as the basis for the refusal.

"I find it frustrating that, despite public statements professing cooperation and an expressed desire to resolve the various investigations that it faces following its calculated deception, Volkswagen is, in fact, resisting cooperation by citing German law," Mr Jepsen said in a statement.

Car industry record year

In 2015, a record 17.47 million cars were sold, according to Autodata. The car data firm has been keeping records since 1980.

General Motors, one of the biggest US car firms, had an 8% increase in sales.

Mercedes-Benz USA had its most successful year since entering the country, with sales rising 3.8%.

The UK also had a record year for car sales. According to the Society of Motor Manufacturers and Traders, 2.63 million cars were registered, beating the previous record from 2003.