President Obama used the word “scuffles” to describe the invasion of Ukraine while maintaining that his No. 1 security concern is a rogue nuclear weapon detonating inside the U.S. instead of Russia.

Obama was eager to stay on the nuke topic at a press conference with Dutch Prime Minister Mark Rutte after the conclusion of the Nuclear Security Summit in The Hague. Foreign and American media alike, though, wanted to talk Russia after the G-7 met on the sidelines of the conference to take their caucus down by one member.

Russian Foreign Minister Sergei Lavrov showed up for the class photo at the end of the summit, but stood rows away from Obama.

Obama said he was “less interested” in President Vladimir Putin’s motivations for taking control in Eastern Europe than “the facts and the principles that not only the United States, but the entire international community are looking to uphold.”

“I don’t think that any of us have been under any illusion that Russia has been very interested in controlling what happens to Ukraine. That’s not new. That’s been the case for years now. That’s been the case dating back to the Orange Revolution,” he added.

“It is now up to Russia to act responsibly and show itself to be, once again, willing to abide by international rules and international norms. And if it chooses to do so, I think that there could be a better outcome. If it fails to do so, there will be additional costs. And those will have some disruptive effect to the global economy, but they’ll have the greatest impact on Russia.”

The G-7 agreed on sectoral sanctions that could be kicked into effect if Putin starts to grab more territory than Crimea.

A foreign reporter asked Obama what “guarantees” he could give to other countries in Eastern Europe that they wouldn’t be next on the land-grab list.

Obama said the seizure of Crimea isn’t a “done deal” as “history has a funny way of moving in twists and turns, and not just in a straight line.”

“So, you know, how the situation in Crimea evolves in part depends on making sure that the international community stays unified in indicating that this was an illegal action on the part of Russia,” he said. “With respect to the Russian troops that are along the border of Ukraine at the moment, right now they are on Russian soil. And if they stay on Russian soil, we oppose what appears to be an effort at intimidation. But Russia has the right, legally, to have its troops on its own soil.”

Obama brushed off Russia’s assertion that Russian speakers within Ukraine have faced any sort of threats that justify action by Moscow. “If anything, what we’ve seen are provocateurs who have created, you know, scuffles inside of Ukraine,” he said.