WASHINGTON (Reuters) - U.S. President Donald Trump said on Wednesday NATO countries must immediately pay 2 percent of their country’s economic output for defense, tying the issue to trade and energy in a Twitter post as he attended the alliance’s summit in Brussels.

Trump earlier told alliance leaders they should raise their defense spending to 4 percent of their gross domestic product, or GDP.

“What good is NATO if Germany is paying Russia billions of dollars for gas and energy?” Trump wrote. “The U.S. is paying for Europe’s protection, then loses billions on Trade. Must pay 2% of GDP IMMEDIATELY, not by 2025,” he added.