U.S. President Donald Trump said Saturday that Iran will face more military strikes if peace does not come quickly.

Addressing the nation Saturday evening, Trump said that Iran's key nuclear facilities had been "completely and totally obliterated," and that future attacks will be "far greater and a lot easier."

"If peace does not come quickly, we will go after those other targets with precision, speed and skill. Most of them can be taken out in a matter of minutes," he said.

"Our objective was the destruction of Iran's nuclear capacity," he said, calling the bombing a "spectacular" success.

Trump said that he decided a long time ago not to let Iran gain a nuclear weapon and that without peace, there will be "tragedy" for Iran that will far exceed what's taken place.

Top U.S. military leaders will hold a news conference at 8:00 am (1200 GMT) Sunday morning, he said.

Meanwhile, UN Secretary-General Antonio Guterres said Saturday that U.S. strikes on Iran's nuclear sites are "a dangerous escalation" and "a direct threat to international peace and security."

"I am gravely alarmed by the use of force by the United States against Iran today. This is a dangerous escalation in a region already on the edge -- and a direct threat to international peace and security," said Guterres in a statement.

There is a growing risk that this conflict could rapidly get out of control -- with catastrophic consequences for civilians, the region and the world, he said.

Guterres called on UN member states to uphold their obligations under the UN Charter and other rules of international law.

"At this perilous hour, it is critical to avoid a spiral of chaos. There is no military solution. The only path forward is diplomacy. The only hope is peace," he said.