LONDON (Reuters) – The sovereign right of the Ukrainian people to join NATO cannot be traded away, British Prime Minister Boris Johnson said on Monday, adding he would be talking to U.S. President Joe Biden “very soon” to help the diplomatic process. “I think it is very important that we have a conversation. But what we can’t do is trade away the sovereign rights of the Ukrainian people to aspire to NATO membership… you can’t bargain that away – it is for the Ukrainian people,” Johnson said. “We have got to realise that this is a very, very dangerous, difficult situation. We are on the edge …