SILVERSTONE, England, July 6 (Reuters) - Prodrive boss David Richards, whose company is due to enter Formula One as the 12th team next year, said on Friday he was still some way from announcing details of his plans.

The former BAR and Benetton team boss told reporters in Bahrain in April he hoped to make a full announcement on sponsors and drivers before Sunday's British Grand Prix.

"It would be nice to have something to announce by now but the truth of the matter is we are a few weeks away from sorting a few issues out," said Richards after Friday's free practice at Silverstone.

"There will definitely be nothing this weekend."

Richards said talks with potential sponsors were well advanced.

"It's all very well people agreeing things and signing heads of terms but you need to get them properly contracted before you go formal on anything," he added.

"The issue is making sure we have got robust contracts in place."

Richards has made no secret he plans to use a chassis and engines provided by a major manufacturer, with championship leaders McLaren seen in the Formula One paddock as the most likely option.

Formula One's technical rules are due to change next year, allowing teams to race cars they have not built themselves. At present they must own the intellectual property to their own chassis.

"I'm not going to comment on who the partners are ... but we have a favoured partner and are working exclusively down that direction," said Richards.