President Trump told senior aides late Tuesday that he approved of attack plans for Iran, but was holding off to see if Tehran would abandon its nuclear program, people familiar with the deliberations said.

In the Middle East, Israel and Iran continued to exchange fire as the conflict entered a seventh day. An Israeli hospital was hit by an Iranian missile, while Israel said it struck 100 targets in Iran, including the heavy-water reactor in Arak and a site in Natanz that it said was being used for nuclear-weapons development.

Asked if he had decided whether to strike at Iran’s nuclear facilities, Trump said, “I may do it, I may not do it.” And he repeated his insistence on Iran’s unconditional surrender: “The next week is going to be very big, maybe less than a week.”

The U.S. has built up military forces in the region in recent days. A third U.S. Navy destroyer entered the eastern Mediterranean Sea and a second U.S. carrier strike group is heading toward the Arabian Sea. While the Pentagon said the buildup is defensive, it better positions the U.S. should Trump decide to join Israeli attacks on Iran. It could also be a tactic to pressure Iran to capitulate or make concessions.

Israeli Prime Minister Benjamin Netanyahu called an Iranian strike on a hospital the work of “terrorist tyrants” and said Israel is advancing “step by step” toward eliminating Iran’s nuclear program and ballistic missiles.

The U.N.’s atomic agency said there was no radioactive spill from Iran’s Khondab heavy-water research reactor, formerly known as Arak, after an Israeli strike on the facility.

The U.S. Embassy in Israel is arranging evacuation flights for American citizens seeking to leave the country, said Mike Huckabee, the U.S. ambassador to Israel.

The death toll in Iran rose above 639 people, according to a human-rights group. In Israel, 24 people have died as a result of Iranian strikes.