Republican Congressman Justin Amash trolled U.S. President Donald Trump and his son on Twitter Thursday.

Amash and Trump are feuding amid reports that Trump is looking to recruit a primary opponent for Amash due to his support for launching impeachment proceedings.

Amash tweeted a reply to Trump Jr., writing, “if it's what you say I love it especially later in the summer.” Amash was replying to a tweet from Trump Jr. which said, “See you soon Justin... I hear Michigan is beautiful during primary season.” CNBC reported earlier that Trump’s son is planning to campaign against the only Republican congressman who has called for Trump’s impeachment.

Trump Jr., the eldest son of Trump, appeared for a closed-door interview with the Senate Intelligence Committee on Wednesday and then told reporters his responses were the same as during a 2017 appearance before the committee.

The interview had been expected to focus on a Moscow Trump Tower project and a meeting with a Russian lawyer who claimed to have information helpful forTrump Sr.'s 2016 presidential campaign. Trump Jr. email exchange which set up the meeting under scrutiny included the line Amash used, “if it's what you say I love it” - in reference to Russians having damaging information on Hillary Clinton.

"I don't think I changed anything of what I said because there was nothing to change," Trump Jr. told reporters after the Senate interview. "I'm glad that this is finally over. We were able to put some final clarity on that and I think the committee understands that."

Asked if he was worried about potentially perjuring himself, he said: "Not at all."

The Senate committee, which is chaired by Republican Senator Richard Burr, is conducting a bipartisan investigation into Russian interference in U.S. politics, including the 2016 U.S. presidential election.

The Senate investigation continues although Special Counsel Robert Mueller has concluded his inquiry into whether the Trump campaign colluded with Moscow and possible obstruction of justice by the president.

The appearance by Trump Jr., who now heads the Trump Organization with his brother Eric, was expected to cover a wide array of subjects, including the Moscow Trump Tower project. Trump Jr. had previously testified in front of a different panel, the Senate Judiciary Committee, that he was only "peripherally aware" of the project.

But Michael Cohen, the president's former lawyer, contradicted Trump Jr.'s testimony.

The Russia project never came to fruition but is considered significant because it shows the president and his company were chasing a lucrative business deal in Moscow while the Russian government, according to U.S. intelligence agencies, was conducting a hacking and propaganda campaign to boost his candidacy.

Trump initially denied he had any business links to Russia at the time.

Cohen, who is currently serving a prison sentence after pleading guilty in two federal cases, also told Congress that Trump Jr. and the Trump Organization's chief financial officer signed some reimbursement checks for hush-money payments made to a porn actress who said she had an affair with Trump.

The senators also were expected to question Trump Jr. about a June 2016 meeting he and campaign advisers Paul Manafort and Jared Kushner held at New York's Trump Tower with a Russian lawyer.

The lawyer had promised to share damaging information on Trump's 2016 opponent, Hillary Clinton, although in fact, little useful information was shared.

Trump Jr. agreed to appear for the committee interview after the panel issued a subpoena for his testimony. The subpoena was criticized by some of the president's most vocal defenders within his Republican Party.