Motor racing-Rosberg in high speed blowout

* Mercedes driver unhurt after Bahrain blowout * Pirelli say type of tyre will not be used again * Supplier assures teams 2014 tyres will be safe (Adds Pirelli statement) Dec 19 (Reuters) - Pirelli assured Formula One teams that next year's tyres would be safe after Mercedes driver Nico Rosberg escaped unhurt from a high speed blowout during private testing in Bahrain on Thursday. "Just spun at full speed 320km/h on Bahrain straight cause my tyre blew up without warning," the German said in a tweet that was later deleted. "Thanks to that need to get some toilet paper now." Four of the 11 teams are taking part in a three-day test with tyre supplier Pirelli, following changes to sporting regulations on safety grounds, to try out prototypes for the 2014 season. While regular testing is banned until next year under current rules, Pirelli had called for a dispensation so they could collect more data about the tyres with representative machinery. The Italian company is keen to avoid any repeat of this year's spectacular British Grand Prix blowouts that threw the sport into crisis and forced Pirelli to revise their tyre construction. Pirelli said in a later statement that the tyre that failed Rosberg was innovative in terms of structure and compounds, had only been tested previously in the laboratory and would not be used again. "The safety of the tyres which will be supplied for the next championship is not in question," the Italian supplier added. Pirelli said Rosberg's accident was being investigated and the governing FIA and all teams would be informed of the findings. (Reporting by Josh Reich/Alan Baldwin, editing by Justin Palmer)