Sources told Bloomberg that the United States is preparing a new round of sanctions on Russia’s energy sector to increase pressure on Moscow if President Vladimir Putin refuses to reach a peace agreement with Ukraine.

The sources said Washington is considering measures including targeting ships in Russia’s so-called “shadow fleet” of oil tankers, as well as traders facilitating Russian oil transactions.

They added that the new measures could be announced early this week, noting that Treasury Secretary Scott Beissinger discussed the plans with a group of European ambassadors earlier this week.