The administrator of the Panama Canal has responded to criticisms from U.S. President-elect Donald Trump, denying that there is any interference from China in the canal’s operations and saying giving special privileges to any nation would only cause problems.

Treaties ratified by the Senate in 1978 established permanent neutrality, but some Republicans regret that decision.

If commercial fees are typically low and America’s navy already has cheap and preferential access, why is Mr Trump threatening to take the canal? The simplest answer may be that the president-elect is expressing geopolitical machismo,