Ford has vowed to hang on to Land Rover and Jaguar despite a mixed month for the two marques in the vital US market.

Sales of Jaguar's XJ saloon were almost wiped out during September after a delivery problem prevented cars reaching the showrooms, while Land Rover edged ahead.

The Solihull 4x4 maker notched up a one per cent sales increase in the month, as the number of vehicles sold increased from 3,425 to 3,469.

Strong sales of the Range Rover Sport, which increased by a quarter last month, helped to boost overall figures in the year to date by eight per cent to 33,527.

Success for Jaguar's XK sports car, which is built at the Castle Bromwich factory in Birmingham, contrasted with a disastrous month for the XJ saloon.

The XK exceeded expectations with sales more than doubling from 138 last September to 311 last month, while in the year to date it was 73 per cent ahead at 3,354 cars.

But the XJ saw sales plummet 96 per cent - a figure attributed to cars not being released from storage depots in America while the company waited for parts to be delivered.

Only 33 cars were sold in the month, compared with 827 in September 2007, and Jaguar said it was working on the problem.

Meanwhile the X-type fell by 32 per cent to 412 cars sold, and the S-type slumped 29 per cent to 402 cars in the month.

The downturn meant Jaguar sales were 46 per cent down at 2,135 cars, and 32 per cent adrift in the year to date at 16,508.

A spokesman for Jaguar said: "We are in an extremely competitive market, and we are still in the process of refocussing the company's position, which has had some impact on sales.

"This is one month's sales figures, and there is one clear reason why they are down. The XK is the pointer to the future, and that enjoyed a particularly strong month.

"But the XK has had a strong performance which is showing the way ahead."

Some relief came for Jaguar's fortunes yesterday when the company notched its biggest single fleet deal in the Middle East.

The contract to supply 100 long wheel base XJ saloons to the Transport Company, a chauffeur operator in Qatar, is estimated to be worth at least £5 million.

Ford overall enjoyed a brief respite from its troubles in September, with overall sales up 4.7 per cent at 228,000, although the firm was 8.5 per cent down in the year at 2,287,000 vehicles.

There had been speculation the Jaguar and Land Rover could be sold by Ford, which is looking at all its business including the sale of Aston Martin.

Meanwhile it has emerged that Aston Martin supremo Ulrich Bez is in favour of the sell-off of the luxury carmaker, although he has ruled out a management buy out.

During the Paris Motor Show last week Dr Bez was heard to liken the situation to a child growing up and leaving its family.

The auction for Aston Martin is thought to have attracted so many expressions of interest that Ford has imposed an extra round of bidding in order to filter out the serious interest.

Among those with a firm interest are understood to be One Equity, the private equity arm of JP Morgan, where former chief executive Jac Nasser is a senior partner.

Cereberus, the New York private equity group which employs David Thursfield , former head of Ford's international operations, is also thought to be eyeing the sale, as is the Magma group headed by LDV chairman Martin Leach.

A spokesman for PAG declined to confirm any of the bidders, but said: "We always said from the beginning we are looking at a partial or complete sale of the business or it could be the case this evaluation will not lead to a sale at all. Jaguar and Land Rover are not for sale."