President Trump is reportedly telling advisers he might temporarily shelve a plan to pursue a deal with Russia on how to handle the Islamic State as well as other national security matters.

Administration officials and Western diplomats told the Associated Press on Saturday that Trump and his aides have ascribed the new thinking to Moscow’s recent provocations, including deploying a cruise-missile which violates a Cold War-era arms control treaty.

Trump has been pressured by members of his Cabinet, including Defense Secretary Jim Mattis and new national security adviser H.R. McMaster, and European allies to not give concessions to Russia.

In his first meeting with the National Security Council staff, McMaster described Russia – as well as China – as a country that wants to upend the current world order, an administration official told AP.

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European officials have tailored their rhetoric to appeal to Trump's business background, including emphasizing the risks of negotiating a bad deal, rather than more nuanced arguments to bolster their case about Moscow and Russia’s intentions, according to one Western diplomat.

Trump reportedly sent letter to Eastern European leaders, who worry Russia might set its sights on their borders next, underscoring his commitment to their security.

Your support for the sovereignty and territorial integrity of Ukraine is important for our shared goal of enhancing European and regional security," Trump wrote to the Estonian president in a letter dated Feb. 15 and obtained by The Associated Press.

Michael McFaul, who served as President Barack Obama's ambassador to Russia, said that while Trump has been open about wanting warmer relations with Russia, "he hasn't picked people to the best of my knowledge at senior levels that share that view."

Trump, who spoke favorable of Russian President Vladimir Putin during his campaign, is said to have shown interest in a broad deal with Russia that could address cooperating in fighting the Islamic State, nuclear arms control agreements and Russia’s provocations in Ukraine.

In recent days, however, the tone has been different. The administration has signaled that the oment for such a deal may not be right as long as the FBI investigates Trump’s campaign associates’ possible connections to Moscow and congressional committees step up their inquiries into Russia’s meddling in the 2016 election.

A White House official said Russia’s violation of the Cold War-era treaty has taken a toll on Trump and has altered his view on relations with Russia. The official said that Trump believes the violation is making a diplomatic and security agreement with Russia “tougher and tougher to achieve.”

Trump has been trailed by questions about his possible ties to Russia for months. He's taken an unusually friendly posture toward Russia, praising Putin's leadership and, at times, appearing to echo Kremlin positions on Ukraine and other matters.

He's also repeatedly said that it would be better for the U.S. and Russia to have a stronger relationship, particularly in fighting terrorism.

Trump has insisted that he has no nefarious connections or financial ties to Russia. He's also said he's not aware of any contacts his campaign advisers had with Russia during the 2016 campaign, a period in which U.S. intelligence agencies assess Russia was interfering with the election to help Trump defeat Democrat Hillary Clinton.

Still, the suggestions of wrongdoing have followed Trump to the White House, in part because of his own team's missteps. Flynn was fired for misleading Vice President Pence and other top White House officials about the nature of his conversations with Russian Ambassador Sergey Kislyak, even as the FBI was interviewing Flynn about those contacts.

The Associated Press contributed to this report.