Sources -- Vasiliy Lomachenko's team seeks OK to train for proposed George Kambosos fight outside Ukraine

As Vasiliy Lomachenko works to help defend Ukraine from Russia's ongoing invasion, efforts are being made by his team to allow him to leave his native country to train for a proposed fight against undisputed lightweight champion George Kambosos, sources told ESPN.

Lomachenko, 34, joined a territorial defense battalion earlier this month and has been working on a security detail at the Ukraine-Russia border, sources told ESPN. Under martial law in Ukraine, able-bodied men between the ages of 18 and 60 are prohibited from leaving the country to aid in defense against Russia.

Lomachenko, a former three-division champion and two-time Olympic gold medalist, agreed to a deal in February to fight Kambosos on June 5 in Melbourne, Australia. Lomachenko was in Greece but returned to Ukraine shortly after the Russian invasion began.

Kambosos (20-0, 10 KOs) hasn't agreed to a deal yet, according to sources, but he is closing in on a pact with promoter Lou DiBella for a title defense at Marvel Stadium, whether it's against Lomachenko or Devin Haney, the rising star who remains in the mix for the assignment.

Officials involved with the bout require that a Kambosos opponent be locked in by the end of March to allow for the typical eight-week promotional push, sources said. If there's no clarity regarding Lomachenko's ability to leave Ukraine and set up training camp by next week, talks will intensify with Haney, who is promoted by Eddie Hearn, according to sources.

However, Lomachenko (16-2, 11 KOs) remains Kambosos' focus. If the fight happens, it will take place on a Sunday afternoon in Australia to accommodate a prime-time ESPN telecast stateside on Saturday.

Lomachenko, ESPN's No. 7 pound-for-pound boxer, has reeled off two