The United States has slowed the sale of Russian oil giant Lukoil’s international assets to pressure Russia in the Ukraine peace talks, according to four sources familiar with the discussions, writes Reuters.

“On Thursday, the U.S. Office of Foreign Assets Control will extend the February 28 deadline to April 1 for deals to be concluded, an OFAC document reviewed by Reuters showed. U.S., Russian and Ukrainian government officials have not made a breakthrough in talks in Geneva, Abu Dhabi and Miami in recent weeks to negotiate a peace deal in Ukraine. These discussions included the U.S. sanctions on Russia’s top oil producer, state-run Rosneft, as well as on second-largest producer Lukoil, according to three sources who were briefed on the meetings.

The next round of talks between the U.S., Russia and Ukraine is planned for March.

OFAC has already extended the deadline three times for potential buyers to negotiate with Lukoil for assets valued at $22 billion since Washington imposed sanctions on the two Russian oil companies in October.

A U.S. official said the Treasury extended the deadline to “facilitate ongoing negotiations with Lukoil and to reach a deal that supports President (Donald) Trump’s efforts to deprive Russia of the revenue it needs to support its war machine and to achieve peace”.

Any deal requires that Lukoil receives no upfront value and that all sale proceeds be placed in an account where funds are frozen and subject to U.S. jurisdiction, the official said”.