China is withholding approval for a planned visit by Elbridge Colby, the Pentagon's top policy official, until the Trump administration makes a final decision on a $14 billion arms package for Taiwan, people familiar with the discussions told the Financial Times, raising fresh tensions at an already fragile moment in US-China relations.Colby's Beijing Visit: What We KnowElbridge Colby, the US under-secretary of defence for policy, has been in discussions with Chinese officials about a summer visit to Beijing.However, China has signalled it cannot approve the trip until Washington resolves the question of the pending weapons package, which includes Patriot interceptor…