European countries on Monday demanded to know more about U.S. President Donald Trump’s plans for the war on Iran and when the conflict might end as they weighed whether to agree to his call to send warships to help shore up security in the Persian Gulf.

Trump has asked allies — including France, China, Japan, South Korea and Britain — to help secure the strait for global shipping. He said the U.S. was talking to “about seven” countries for military support to help reopen the trade route. But he wouldn’t say which ones and gave no indication of when such a coalition might be formed.

Separately, in an interview with the Financial Times, he warned that “if there’s no response or if it’s a negative response I think it will be very bad for the future of NATO.”

As European Union foreign ministers gathered to discuss Trump’s demand, German Foreign Minister Johann Wadephul said it’s important for the United States and Israel to define “when they consider the military aims of their deployment to have been reached.”

“We need more clarity here,” Wadephul told reporters.