Secretary of State Marco Rubio laid out the America First doctrine in one sentence on Monday. “Before what is good for another country, before what is good for another continent, it’s what’s good for America,” Rubio said in an interview posted by the State Department. “It has to be. Because if we’re not looking out for our national interest, nobody else is going to.”

Rubio said that is the job of everyone who serves the President. “Ultimately the job of the President of the United States and all of us who work for him is to make sure that the national interest of the United States is foremost before anything else,” he said. He expects other nations to do the same, “like I expect the Colombian government to put as their priority the national interest of Colombia.” And if it ever comes down to a conflict, he said, “we always have to be for what’s good for us.”

He applied that rule to the President’s decision on diesel. With the world economy needing a bigger diesel supply, Rubio said, the President chose once again to pause sanctions so more Russian diesel can reach the global marketplace. “That will impact and help the United States,” Rubio said. “And that’s a decision he made not because it’s bad for Ukraine or good for Russia but because it’s good for America and it’s important for America.”

Rubio also gave a clear-eyed picture of the war itself. “This war is honestly about one part of Ukraine called Donetsk,” he said. Russia occupies all but about 11% of that region, where Ukraine holds what it calls its last defensible line. Unable to take it on the battlefield, Rubio said, Russia is pounding Ukraine’s power grid with drones and missiles ahead of winter, while Ukraine is hitting Russian oil and gas refineries. “For the first time Russians are seeing explosions going on in Moscow, in St. Petersburg deep into their territory.”

The United States, Rubio said, “remains willing, able and prepared to play a mediating role if the opportunity presents itself to end this war through a negotiated settlement.” He said it has not been easy, “not for lack of trying because Jared and Steve and others have invested a lot of time into it,” and added: “We are going to keep trying as much as we can to see what we can do.”

It is the same rule President Trump has governed by from day one: America comes first, and everything else comes after.