President Donald Trump warned that "severe consequences" lie ahead for Russia if Russian President Vladimir Putin doesn't agree to stop the Ukraine war after they meet for a high-stakes summit in Alaska on Friday.

President Donald Trump walked into a summit with Russia’s Vladimir Putin pressing for a ceasefire deal and threatening “severe consequences” and tough new sanctions if the Kremlin leader failed to agree to halt the fighting in Ukraine.

In particular, cutting off the “shadow fleet” of tankers that deliver Russia’s oil under the radar would send the war economy into a “deep financial crisis,” according to Robin Brooks, a senior fellow at the Brookings Institution and former chief economist at the Institute of International Finance.

EXCLUSIVE: Volodymyr Zelensky "would never would want to be the president that gives a fifth of his country to a bully", an expert said.

Ukrainian President Volodymyr Zelenskyy says he will meet U.S. President Donald Trump in Washington on Monday after a Russia-U.S. summit concluded without an agreement to stop the fighting in Ukraine after 3 1/2 years.

The meeting represented a diplomatic victory for Putin after Western leaders ostracized him at the start of Russia's full-scale invasion of Ukraine. Just a week earlier, Trump was threatening him with new sanctions.

In Pew's poll, Trump's current job approval rating stands at 38 percent, with 60 percent of U.S. adults expressing disapproval of his performance. That is a modest decline from two months ago, when 41 percent approved. In January, his approval rating stood at 47 percent.

The White House has increasingly touted Trump's attempts to forge international peace agreements. His meeting with Vladimir Putin in Alaska will be his biggest test by far.