Sullivan was appointed to his current position by Trump in 2017 and was confirmed by the Senate with 94 votes out of 100. During the confirmation hearing, he emphasised his harsh stance towards Russia, including on the alleged interference in the 2016 election, which Moscow vehemently denies.
At the same time, he doesn't have much experience in communicating with Russia, apart from recently meeting with Russian Deputy Foreign Minister Sergei Ryabkov to discuss arms control in light of the US withdrawal from the Intermediate-Range Nuclear Forces (INF) Treaty.
If he is successfully approved by the Senate this time, the deputy secretary of state will be replacing Ambassador Jon Huntsman Jr., who is scheduled to leave his post on 3 October 2019. Earlier, a CNN report, citing two officials from the administration, suggested that Trump would nominate Stephen Biegun, US special representative for North Korea, to Huntsman's position.
Sullivan's alleged potential nomination comes as relations between the two countries are at a low point. The US accuses Russia of meddling in its 2016 presidential election, something that Moscow denies, and of alleged aggressive actions against Ukraine. Washington has imposed several rounds of sanctions against Russia under the pretext of these accusations.