President Trump is expected to discuss defence with Theresa May when he visits Britain next month Evan Vucci/AP

The Trump administration is urging Britain to contribute more towards Nato even though it already meets the alliance’s defence spending target.

The American president appears keen for his closest ally to increase expenditure above 2 per cent of GDP as part of a wider effort to make Europe contribute more towards the alliance, according to a senior source.

The White House push is being used in Whitehall to put pressure on Philip Hammond to increase defence spending. The chancellor is set for a showdown with Gavin Williamson, the defence secretary, next week over how to fund a blueprint for the military, two sources said.

It is understood that Mr Williamson needs Mr Hammond, a former defence secretary, to commit to a significant increase in defence…