NATO Secretary General Mark Rutte warned Thursday that Europe’s declining refining capacity could leave the alliance vulnerable during a major conflict, particularly if Russia were to attack a NATO member.

Rutte raised the concern during an interview with Bloomberg as European officials were objecting to possible U.S. restrictions on diesel exports. He said Europe is not building new refineries while existing facilities are being shut down, creating a strategic vulnerability if the continent suddenly needs large quantities of fuel for military operations.

“If war breaks out, if the Russians would attack and we have to defend ourselves, we need massive amounts of diesel and other oil products for our F-35s, our fighter jets, for our tanks, etc.,” Rutte said. “And that is a big worry.”

The warning comes as diesel supplies remain under pressure globally. Diesel prices have reached record levels amid disruptions tied to conflicts in Iran and Ukraine, while damaged refineries and reduced exports have tightened supplies. Reuters reported that global diesel markets have limited spare capacity to respond to further disruptions.

Rutte was asked specifically about the possibility of the United States restricting diesel exports, but he declined to weigh in on the European Union’s position, saying it would not be helpful for him to comment directly on the bloc’s dispute with Washington.

The European Commission has expressed concern about potential U.S. restrictions, saying disruptions could negatively affect both sides and urging Washington and Brussels to consult before taking measures affecting shared fuel markets. The Trump administration has discussed restrictions as an alternative to an outright export ban, while Energy Secretary Chris Wright has argued that a blanket ban could create additional problems for U.S. refineries and other fuel markets.

Rutte’s comments broadened the issue beyond the immediate fuel-price dispute, highlighting the military implications of Europe’s dependence on refining capacity and imported petroleum products. NATO would require substantial supplies of diesel and other refined fuels to sustain aircraft, armored vehicles, and other military equipment during a prolonged conflict.