President Trump privately voiced frustration on Russia-related matters in phone calls with two GOP senators.

Politico reported Wednesday that Trump railed against a measure imposing fresh sanctions on Russia in a call with Sen. Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (R-Tenn.), the chairman of the Senate Foreign Relations Committee, last month.

Trump said that bill would violate the Constitution and hurt his authority as president, according to Politico. Corker reportedly told the president that the sanctions would, in fact, pass through the House and Senate with bipartisan support.

A spokesperson for Corker confirmed a relevant call but not the details of what was discussed.

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“In late July after the legislation had already passed the Senate, Senator Corker and President Trump had a productive conversation about the congressional review portion of the Russia sanctions bill," the spokesperson told The Hill.

Trump unenthusiastically signed the sanctions bill into law earlier this month.

In a separate call with Sen. Thom Tillis Thomas (Thom) Roland TillisGrassley, Ernst pledge to 'evaluate' Trump's Supreme Court nominee Trump to include North Carolina in offshore drilling moratorium, senator says Biden's six best bets in 2016 Trump states MORE (R-N.C.) on Aug. 7, Trump brought up a bill that Tillis is working on with Sen. Christopher Coons Christopher (Chris) Andrew CoonsMurkowski: Supreme Court nominee should not be taken up before election Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE (D-Del.) that would bar the president from directly firing Robert Mueller, the special counsel investigating possible collusion between the members of the Trump campaign and Russia's efforts to influence last year's presidential election.

Trump reportedly voiced dissatisfaction with that measure, according to Politico.

The White House declined to comment on the phone calls, saying in a statement to Politico: "We do not comment on private conversations the President has with members of Congress. We are committed to working together on tax relief, border security, strengthening the military, and other important issues."

The calls are only the latest sign of rising tensions between Trump and congressional Republicans ahead of a crucial September, when lawmakers must pass a spending bill to avoid a government shutdown and raise the nation’s debt limit.

But the summer has seen the White House hit by a series of controversies and the president publicly feud with Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellGraham: GOP will confirm Trump's Supreme Court nominee before the election Trump puts Supreme Court fight at center of Ohio rally The Memo: Dems face balancing act on SCOTUS fight MORE (R-Ky.).

In an Aug. 9 call with McConnell, Trump is said to have also accused McConnell of failing to protect him from the ongoing Russia probes.

On Wednesday, the White House said McConnell and Trump “remain united” in pursuing the GOP’s agenda.

Trump has publicly shared frustration with the Russia investigations and has repeatedly denied any wrongdoing. He has claimed that the probes are politically motivated, calling them a "witch hunt."

Jordain Carney contributed to this report which was updated at 7:22 p.m.