President Donald Trump, fresh off announcing a cease-fire between Israel and Iran, traveled to The Hague, Netherlands, on Tuesday for the North Atlantic Treaty Organization (NATO) annual summit, a conference where he hopes to score another foreign policy victory by pressing European leaders to increase defense spending.

It will be the first time Trump has faced off with America's European allies since returning to the White House in January.

On the way to the meeting, in a meeting with reporters aboard Air Force One, Trump questioned a core principle of the alliance by refusing to commit to Article 5, the collective defense agreement among NATO countries.

“Are you committed to Article 5 of NATO?” he was asked repeatedly.

"It depends on your definition. There are numerous definitions of Article 5. You know that, right?" Trump said.

“But I am committed to being your friend,” he added. “You know, I've made friends with many of those leaders, and I'm committed to helping them.”

“Are you still committed to mutual defense?” he was asked.

“I'm committed to saving lives,” Trump said. I am committed to life and safety, and I will give you an exact definition when I get there. I just don't want to do it in the back of an airplane.

Trump arrives at the conference with a key priority: He wants the alliance to codify an increase in defense spending across all member nations, from 2 percent of their gross domestic product to 5 percent.

On the eve of Trump's departure, Iran carried out retaliatory attacks against a US base in Qatar. Trump said Monday that 13 of those missiles were intercepted and that a 14th missed.

“I am pleased to report that no Americans were harmed and virtually no damage was done,” Trump posted on social media, adding that Iran gave the United States advance notice.

The trip will be brief. Trump is expected to leave the White House on Tuesday and return to the United States on Wednesday night. Upon his arrival in the Netherlands on Tuesday night, Trump will be in action. He will attend a formal dinner at the Royal Palace of the Netherlands alongside the King and Queen of the Netherlands. He will also take a NATO family photo that evening.

On Wednesday, Trump will attend the NATO summit, where he will participate in a family photo, a photo at the beginning of NATO Secretary General Mark Rutte's speech, and then the first plenary session with NATO leaders.

The president will spend several hours in bilateral meetings, although it is not yet known which leaders he plans to meet with on the sidelines of the summit.

Trump will hold a press conference where he is likely to answer questions about his order to strike Iran's nuclear facilities and the impact of that mission.

After the press conference, Trump will leave the Netherlands and return to the United States.