According to Democratic U.S. Senator Chris Coons, the White House is planning to put a restriction on Russian oil shipments to the United States as retribution for the invasion of Ukraine.

Coons told CNN that the ban might be announced on Tuesday or Wednesday, while a person familiar with the discussions told Reuters that the ban could be announced on Tuesday. President Joe Biden was scheduled to make a sanctions statement at 10:45 a.m., according to the White House (1545 GMT).

Russia is the world’s biggest exporter of oil and natural gas, and until now its energy exports had been exempted from international sanctions. Although the United States is not a leading buyer of Russian oil, its allies are likely to come under pressure to wean their economies off Russian energy.

The announcement will intensify the impact of the war on a global economy already suffering supply shortages and price surges as it lurches out of the pandemic crisis. In the United States, gas pump prices have already surged to a record since Russia launched the invasion on Feb. 24, worsening inflation that was already at 40 year highs.

In Ukraine, Kyiv accused Moscow of shelling a humanitarian corridor it had promised to open to let residents flee the besieged port of Mariupol, where hundreds of thousands of people have been sheltering under relentless bombardment without water or power for more than a week.

“Ceasefire violated! Russian forces are now shelling the humanitarian corridor from Zaporizhzhia to Mariupol,” Ukraine’s foreign ministry spokesperson Oleg Nikolenko wrote on Twitter, adding that 30 buses had been sent for evacuations.

“Pressure on Russia MUST step up to make it uphold its commitments.”

Ukraine’s President Volodymyr Zelenskiy said a child had died of dehydration in Mariupol because water was cut off. The claim could not be independently verified.

Russia opened a separate corridor allowing residents out of the eastern city of Sumy on Tuesday, the first successful evacuation under such a safe route.

Buses left Sumy for Poltava further West, only hours after a Russian air strike, which regional officials said had hit a residential area and killed 21 people. Russia denies targeting civilians.

The number of refugees who have fled Ukraine had surged past 2 million, in what the United Nations describes as one of the fastest exoduses in modern times.

Residents were also leaving the town of Irpin, a frontline Kyiv suburb where Reuters journalists had filmed families fleeing for their lives under fierce bombardment on Sunday. Residents ran with children in strollers or cradling babies in arms, while others carried pets and plastic bags of belongings.

“The city is almost ruined, and the district where I’m living, it’s like there are no houses which were not bombed,” said one young mother, holding a baby beneath a blanket, while her daughter stood by her side.

Moscow describes its actions in Ukraine as a “special operation” to disarm its neighbour and unseat leaders it calls neo-Nazis. Ukraine and its Western allies call this a baseless pretext to invade a country of 44 million people.