European nations worked to keep diplomatic efforts to curb the Israel-Iran war alive as the two countries traded strikes following the United States’ weekend attack on Iran’s nuclear program, followed by a retaliatory Iranian missile strike Monday on a U.

Trump said in a social media post after the attack on Al Udeid Air Base that he wanted Iran to move toward peace talks and that he would encourage Israel to do the same.

The strikes by the U.S. over the weekend raises speculation of how Tehran could respond as President Donald Trump discussed a “regime change″ in Iran.