By Kate Abnett BRUSSELS (Reuters) – The European Commission has warned EU countries that a broad cap on gas prices could be complex to launch and pose risks to energy security, amid calls from countries for Brussels to step in to tame high fuel prices. The Commission shared a document with countries on Wednesday, analysing various options the EU could consider to curb high gas prices, after 15 of the bloc’s 27 member states this week urged the EU to propose a cap on gas prices. The document, seen by Reuters, said a wholesale price cap for exchange transactions – covering both liquefied natural…