US President Donald Trump has addressed the controversy over his eldest son’s meeting with a Russian lawyer during last year’s presidential campaign.

President Trump said that “most people would have taken that meeting”, contradicting his incoming FBI director’s testimony that Donald Trump Jr should have instead alerted authorities.

The president reiterated that his son is a “wonderful young man”.

President Trump continued to downplay the issue, saying that “nothing happened” as a result of the meeting.

The president says the Russian national involved was not a government lawyer.

However, the emails Donald Trump Jr received pitched her as one.

President Trump says the woman is a private lawyer who has “roamed the hallways” of the US Congress.

Earlier, the chairman of the Senate Judiciary Committee said he is sending a letter to Donald Trump Jr to ask him to testify.

Senator Chuck Grassley said he would subpoena the president’s eldest son if necessary.

Senator Chuck GrassleySenator Chuck Grassley, chairman of the Senate Judiciary Committee, is sending a letter to Donald Trump Jr to ask him to testify (Pablo Martinez Monsivais/AP)

The Iowa Republican says he wants Mr Trump Jr to appear “pretty soon”, and it could be as early as next week.

Mr Trump Jr released emails this week from 2016 in which he appeared eager to accept information from the Russian government that could have damaged Hillary Clinton’s campaign.

The panel is investigating Russian meddling in the US election.

Mr Grassley would not say what he wants to hear from the president’s eldest son, but said members aren’t restricted “from asking anything they want to ask”.