The Labour government came into office promising to “use realist means to pursue progressive ends”. US president Donald Trump’s recent actions over Venezuela and Greenland have tested Keir Starmer’s ability to deliver on that promise.

When the prime minister said he had been “a lifelong advocate of international law” there was a reasonable expectation that he would condemn the US action in Venezuela. Some feared that his ambiguity on that issue was a betrayal of progressive values.

However, US action in Venezuela came at a sensitive moment in the UK’s efforts to achieve a progressive end to the war in Ukraine. US cooperation is vital if Russia is to be forced to negotiate a peace that respects the Ukrainian right to self-determination. That means persuading the US to put pressure on Russia – something that would be impossible if Starmer had alienated Trump by condemning his illegal action in Venezuela.

Starmer has shown that he is able to handle Trump’s unpredictable personality. His ambiguity on Venezuela immediately prior to the Paris meeting that agreed security guarantees for Ukraine can be interpreted in these terms. He knew that the progressive strategy on Ukraine was reliant on a delicate alignment of US power.

When it emerged that British forces had helped the US seize a........

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