Tom Williams/Getty Images(WASHINGTON) — Sources with knowledge of the investigation surrounding former Trump campaign chairman Paul Manafort tell ABC News a key focus for congressional investigators is emails between Manafort and his longtime associate Konstantin Kilimnik.

Kilimnik, often referred to in these emails as “KK,” has served as Manafort’s liaison overseas since the mid-2000s. In the past, Kilimnik has been reported as a former Russian army trained linguist.

Kilimnik’s work for Manafort focused mainly on relations with power brokers and government liaisons in both Ukraine and Russia, among other nations.

As reported by The Washington Post, Manafort reached out to Kilimnik to re-establish a relationship with Russian oligarch Oleg Deripaska, dubbed in these emails “OVD.”

Manafort and Deripaska had many financial deals in the past, some of which included disputes over payments.

According to a source with direct knowledge of the exchange, Manafort told Kilimnik to tell Deripaska he could provide briefings on the state of the Trump campaign, in the middle of the presidential race.

The goal of these briefings was for Manafort to fix the damaged relationship with Deripaska and settle past debts. However, a source tells ABC News it does not appear those briefings ever happened.

“It is no secret Mr. Manafort was owed money by past clients after his work ended in 2014. This exchange is innocuous,” a current spokesperson for Manafort told ABC News.

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