President Obama will address the nation Friday morning about the situation in Ukraine, a day after a Malaysia Airlines jet with 298 people onboard was downed in the country's separatist-held East.

On Thursday, the president offered only brief comments on the incident, telling a crowd in Delaware that "the world is watching" reports of the crash.

"It looks like it may be a terrible tragedy," Obama said. "Right now, we’re working to determine whether there were American citizens onboard. That is our first priority. And I’ve directed my national security team to stay in close contact with the Ukrainian government. The United States will offer any assistance we can to help determine what happened and why."

Late Thursday night, White House press secretary Josh Earnest called for an immediate cease-fire in eastern Ukraine to allow international investigators access to the crash site.

And for the first time, the administration suggested a link between the crash and pro-Russian militants operating in the area, noting the incident “occurred in the context of a crisis in Ukraine that is fueled by Russian support for the separatists.”

“It is critical that there be a full, credible, and unimpeded international investigation as quickly as possible,” White House press secretary Josh Earnest said in a statement. “We urge all concerned — Russia, the pro-Russian separatists, and Ukraine — to support an immediate cease-fire in order to ensure safe and unfettered access to the crash site for international investigators and in order to facilitate the recovery of remains.”

A senior administration official said Thursday the focus of U.S. efforts at this point was preparing to support an international effort to find out what happened. Officials from the National Transportation Safety Board and FBI are involved in that work, the official said.

Later Friday, President Obama will meet in the Oval Office with Secretary of State John Kerry and Treasury Secretary Jack Lew — the two administration officials who have played a central role in the development of sanctions toward Russia for its role in the Ukraine crisis.

The U.S. on Wednesday moved to impose a new round of sanctions on Russian energy and defense companies over Russian assistance for the rebels, but the administration could push for greater penalties if it is determined Moscow was directly or indirectly responsible for the downing.