Donald Trump is considering a reduction in intelligence sharing with members of NATO, which depends on the U.S. for the type of information that has helped Ukraine fend off Russia, according to foreign officials informed of the plans.

Trump advisers have told allied countries the reduced intel sharing would be part of a broader plan to scale back U.S. support and cooperation with the 32-nation alliance, according to three European officials and a senior NATO official, who were granted anonymity to discuss internal discussions.

The officials said they learned about the proposal to curb intelligence-sharing during discussions with Trump advisers about broader plans to reduce U.S. involvement with NATO. The former president repeatedly questioned and sought to undercut the alliance during his first term in office.

The curtailment of intel could have dire security consequences, especially for Ukraine as it tries to repel the Russian invasion.

“It’s the American intelligence that helped convince a lot of NATO countries that Putin was resolved to invade Ukraine,” one European official said. “Some countries didn’t believe Russia had the capabilities to carry out a successful military campaign.”

Asked for comment, a spokesperson from the Trump campaign did not respond directly, instead referring to a statement on TruthSocial that the former president “will restore peace and rebuild American strength and deterrence on the world stage.”

The curtailment of intelligence under a possible future Trump administration was a topic of discussion at this week’s NATO summit, according to the officials, as well as a senior U.S. official. All of them were provided anonymity to discuss freely their thoughts about a second Trump administration.

Reducing U.S. intelligence sharing could reduce Europe’s ability to withstand a Russian invasion, should President Vladimir Putin decide to expand military operations on the continent beyond Ukraine, the senior U.S. official said.

President Joe Biden expanded the amount of intel the U.S.shares, particularly related to Russia, with foreign allies. The European officials said it is unclear whether the Trump administration is considering returning to the previous level of intel-sharing or cutting back further.