US President Donald Trump is undergoing medical tests as part of what the White House said was his annual check-up.

The appointment at Walter Reed National Medical Centre was not on Mr Trump’s weekend public schedule that was released on Friday night, and his last physical exam was in February.

Press secretary Stephanie Grisham said the 73-year-old is “anticipating a very busy 2020” and wanted to take advantage of “a free weekend” in Washington to begin “portions of his routine” check-up.

No details of what tests will be carried out were released.

His check-up in February revealed he had put on weight and was officially considered obese, with a body mass index of 30.4.

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The president’s motorcade outside the Walter Reed National Military Medical Centre in Washington (Manuel Balce Ceneta/AP)

Mr Trump spent more than four hours at Walter Reed on February 8 for his most recent check-up, supervised by Dr Sean Conley and involving a panel of 11 specialists.

At the time, White House staff said Mr Trump was in “very good health and I anticipate he will remain so for the duration of his presidency”.

Test results which came out six days later showed he is obese under the commonly used BMI formula.

About 40% of Americans are obese, which raises their risk of heart disease, diabetes, stroke and some forms of cancer.

Mr Trump does not drink alcohol or smoke. His primary form of exercise is golf.

His latest check-up comes as House investigators on Capitol Hill interviewed a White House budget official as part of the impeachment inquiry.