Andy Murray seemingly aimed a dig at United States president Donald Trump as he prepared for the Citi Open.

Murray, who pulled out of Wimbledon following his return from injury, has accepted a wild card to the ATP World Tour event in Washington DC.

And as he trained this week, the Briton appeared to mock Trump's comments on freedom of speech, which include criticism of NFL players not standing for the national anthem.

"Pumped to be back in the big W," Murray posted on Instagram, alongside a picture of him on court in the capital.

"Got to be careful what you say around these parts nowadays, though. #freespeech #fakenews"