The United States is weighing the threat of sanctions against Russian oil companies Rosneft and Lukoil as part of a menu of options to push President Vladimir Putin to accept a ceasefire with Ukraine, Bloomberg News reported Friday, citing people familiar with the matter.

Reuters could not immediately confirm the report. 

Rosneft is a state-owned oil company and one of the largest publicly traded oil companies in the world. Lukoil is Russia's second-largest oil company and one of the largest private oil and gas companies globally.

By considering sanctions on these key companies, the United States appears to be increasing pressure on Russia to engage more seriously in ceasefire negotiations, according to the report.