Sen. Lindsey Graham Lindsey Olin GrahamSenate GOP aims to confirm Trump court pick by Oct. 29: report The Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Senate GOP sees early Supreme Court vote as political booster shot MORE (R-S.C.) on Monday warned President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE to "check the soccer ball" Russian President Vladimir Putin gave him for "listening devices."

"If it were me, I’d check the soccer ball for listening devices and never allow it in the White House," Graham tweeted, referring to the soccer ball Trump threw to his wife at the end of his press conference with Putin. Trump said the World Cup ball was a gift from Putin.

Finally, if it were me, I’d check the soccer ball for listening devices and never allow it in the White House. — Lindsey Graham (@LindseyGrahamSC) July 16, 2018

Graham also said Trump and Putin's joint press conference was a "missed opportunity by President Trump."

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"Missed opportunity by President Trump to firmly hold Russia accountable for 2016 meddling and deliver a strong warning regarding future elections," Graham tweeted.

Trump during the press conference downplayed Russia's interference in the 2016 presidential election despite special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's recent indictment of 12 Russian intelligence officials who hacked U.S. systems.

Trump said he doesn't "see any reason why it would be" Russia who hacked Democrats in 2016, though the U.S. intelligence community's has unanimously concluded the Kremlin interfered in the 2016 election.

He said both the U.S. and Russia are to blame for the poor relationship between the two countries. He blamed Mueller's probe for keeping the countries "separated" and said "there was no collusion at all."

Media figures and lawmakers from both parties have responded to the press conference with outrage and disbelief, with many claiming Trump's denial of Russian meddling amounts to treason.

"This answer by President Trump will be seen by Russia as a sign of weakness and create far more problems than it solves," Graham tweeted after the press conference, joining the ranks of GOP lawmakers who are expressing dissatisfaction with Trump's denial of Russian influence.