Trump Jr's subpoena is the first congressional subpoena issued by the Republican-led Senate to one of the US President's children, according to Axios.
The Committee is reportedly seeking to question Trump Jr about testimony he gave in 2017 to the Senate Judiciary Committee which was contradicted in public testimony by former US President's attorney Michael Cohen, a Reuters report says citing a source.
During an appearance before the Judiciary Committee Trump Jr was asked about the extent of his involvement in a plan to build a Trump Tower in Moscow. At the time US president's son said that he "was peripherally aware of it."
In testimony before the House of Representatives Oversight Committee Trump's ex-attorney Cohen said that he briefed Trump family members "approximately 10 times" about the Moscow Trump Tower project and that Donald Junior and his sister Ivanka were among the family members he briefed, Reuters report says.
The subpoena was blasted by a person close to Trump Jr as "an obvious PR stunt from a so-called 'Republican' senator," CNBC reports says.
"Don and Senate Intel agreed from the very beginning that he would appear once to testify before the committee and would remain for as long as it took to answer all of their questions. He did that. We're not sure why we're fighting with Republicans," Axios reported citing a source close to Trump Jr.
Donald Trump Jr is expected to fight the subpoena, according to CNBC referring to a source.
The 448-page Mueller report summed up the results of the special counsel's 22-month long investigation into allegations that Trump's team conspired with Moscow to influence the outcome of the 2016 election and that the US president had obstructed justice. Mueller's investigation found no signs of collusion between the Trump campaign and Russia, something which has been denied by Moscow from the onset, and found no proof of obstruction — but refused to fully exonerate Trump on this point.
Russia has repeatedly refuted allegations that it meddled in the US presidential election, as well as in any other foreign election.