What is NATO? Trump has a long beef with transatlantic alliance.

According to NATO, the United States also provides intelligence, surveillance and reconnaissance; air-to-air refueling; ballistic missile defense; and airborne electromagnetic equipment.

After Trump’s speech Saturday, NATO Secretary General Jens Stoltenberg said the alliance remains ready and able to defend itself.

“Any suggestion that allies will not defend each other undermines all of our security, including that of the US, and puts American and European soldiers at increased risk,” he wrote in a statement. “I expect that regardless of who wins the presidential election the US will remain a strong and committed NATO Ally.”

Emily Rauhala contributed to this report.