WASHINGTON — The United States is escalating its sanctions against Russia over the Ukrainian crisis, targeting some of Russia's largest companies and individuals tied to Russian President Vladimir Putin.

President Obama will speak publicly on the sanctions at 5:15 p.m. Eastern time.

The companies targeted include Gazprombank, Russia's third largest bank; Vnesheconombank, a bank tied closely to Putin; Novatek, its largest natural gas supplier; and oil giant Rosneft. U.S. are forbidden from issuing new, long-term financing for these companies,, but their assets are not completely frozen.

Also listed are five Russian nationals and 11 Russian and Ukrainian entities whose assets will be frozen. Those other targets include Russian defense concerns including Kalashnikov, the maker of the iconic AK-47 assault rifle, and UralVagonZavod, a major tank maker.

MORE: Full list of sanctions

The Treasury action follows a round of phone calls by President Obama to European leaders — including British Prime Minister David Cameron and German Chancellor Angela Merkel — to ensure their support. In a call with Merkel Tuesday, the two leaders agreed to "take immediate steps to deescalate the situation in eastern Ukraine amid the ongoing violence there," the White House said.

Hours before the announcement, White House Press Secretary Josh Earnest warned that Russia's one-step-forward, two-steps back response to the crisis "put them at risk of greater isolation and greater economic consequences."