NATO Secretary General Jens Stoltenberg has called on European allies to increase defense spending as pressure from U.S. President Donald Trump grows ahead of the alliance summit. The warning reflects renewed strain over how NATO members share the financial burden of collective security.

Stoltenberg’s remarks come as European governments face mounting demands to strengthen their militaries and commit more resources to the alliance. The issue has long been a point of friction in transatlantic relations, with Washington arguing that many allies have not met spending targets.

Trump has repeatedly criticized NATO partners over defense budgets, making burden-sharing a central issue in his approach to the alliance. The latest comments add to a familiar debate over whether Europe is doing enough to support its own security.

The summit is expected to put defense commitments under close scrutiny as NATO members seek to present a united front while managing internal divisions over costs and responsibilities.