President Obama briefly addressed the downed Malaysia Airlines flight before comments this afternoon about infrastructure executive actions in Delaware, saying that the loss of the plane carrying 295 passengers and crew “looks like it may be a terrible tragedy.”

“Right now we’re working to determine whether there were American citizens on board. That is our first priority and I’ve directed my national security team to stay in close contact with the Ukrainian government,” Obama said. “The United States will offer any assistance we can to help determine what happened and why and as a country our thoughts and prayers are with all the families of the passengers wherever they call home.”

His remarks on the flight barely exceeded 30 seconds before he launched into his previously scheduled speech on transportation projects at the Port of Wilmington.

The White House said Vice President Biden called Ukrainian President Petro Poroshenko.

Poroshenko spoke on TV after Obama’s remarks, stressing, “We don’t call this an ‘incident’ or ‘catastrophe,’ but a terrorist action.”

Russian Prime Minister Dmitry Medvedev posted a message on his Facebook page expressing “deepest condolences following the crash of the Malaysian Airlines plane over Ukraine.”

“This tragedy has claimed the lives of hundreds of people from different countries and has caused profound grief for those who lost loved ones,” Medvedev said. “I mourn for the victims.”

State Department spokeswoman Jen Psaki told reporters today that she didn’t have “any confirmed information about casualties, the cause or additional details.”

“Our thoughts and prayers go out to those on board, their families and loved ones. We’re closely monitoring the situation. The secretary is, of course, aware of these reports. And we’re seeking additional information,” Psaki said. “Our embassy in Kiev is also in close contact with the Ukrainian authorities on this incident. But at this point, those are all the details that we have.”

Reports have indicated 23 Americans were on the manifest, but Psaki said they were “looking to, of course, obtain that information.”

Psaki said Secretary of State John Kerry hadn’t called any Russian officials, and she didn’t know of any plans to do so.

Sen. John McCain (R-Ariz.) told CNN that he didn’t want to leap to conclusions about the cause of the crash, but “if it was a missile that took this plane down, then it has to be a very sophisticated weapons system.”

“And the Ukrainians do not have that capability. So if it is the case, we’re going to have to act, and act in the most stringent fashions, including real sanctions, including giving the Ukrainians the ability to defend themselves, which we have not done so far,” McCain said.

“I think Putin was disappointed that he didn’t get more support both in Eastern Ukraine, Odessa, other parts of Southern Ukraine. But most of us who get to know Vladimir figured that he was not was going to give up easily and that he would continue to try to foment disorder in Eastern Ukraine, which, as we all know, is the most important part of the Ukrainian economy,” he said. “So I never believed he was going to go quietly, I’d – it’s impossible to assume that he’d believe that something like this would do anything but have the most negative effects.”

McCain told MSNBC, “If it is the result of either separatist or Russian actions mistakenly believing that this was a Ukrainian war plane, I think there’s going to be hell to pay, and there should be.”