NATO allies fear that a Republican defeat in the US midterm elections could prompt President Donald Trump to intensify pressure on the alliance, according to Politico. European members are increasingly concerned about how the election results might reshape Washington’s foreign policy.

Citing informed sources, the publication reported that Trump could shift his attention toward international affairs if Congress begins restricting his domestic agenda. European officials worry that political setbacks at home might push the US president to take a more confrontational approach toward NATO.

Among the possible measures outlined by Politico are the withdrawal of several thousand additional American troops from Europe, cuts to US financial contributions to NATO and restrictions on the PURL program, which supports weapons purchases for Ukraine. The report also raises the possibility of Washington moving closer to Moscow.

The prospect of a substantial reduction in the American military presence is causing particular concern among European allies. Such a move would leave NATO’s European members struggling to replace capabilities currently provided by the United States.

According to the report, the hardest gaps to fill would involve electronic warfare equipment, air defense systems, intelligence support and aerial refueling capabilities. European countries could also face significant difficulties replacing certain forms of US military logistics assistance.