European governments are sounding the alarm over reports that Washington is exploring a security arrangement with Moscow that allies fear could hollow out NATO and hand Russia a renewed sphere of influence.

Public briefings from European officials describe anxiety that any bilateral understanding between the United States and Russia might trade Ukrainian leverage or eastern flank guarantees for a quick diplomatic win. Capitals that have poured weapons and money into Ukraine's defence say they were not reassured by signals that the White House wants a grand bargain with the Kremlin.

The concern lands days after Democratic midterm gains, when many in Europe hoped Congress would stiffen American support. Diplomats note that foreign policy still runs chiefly through the presidency, so legislative shifts may not block a deal if the White House pursues one.

Allies are pressing for consultation before any text takes shape and for clear red lines on Ukrainian sovereignty and forward defence of NATO members. Without that, they warn, years of military aid and political unity could be spent down in a settlement that freezes the war on Moscow's preferred map.