Sources -- Oleksandr Usyk permitted to leave Ukraine, prepare for title rematch with Anthony Joshua

Oleksandr Usyk and Anthony Joshua are going to run it back this summer.

Usyk received permission to leave Ukraine from the country's sports minister and will begin training camp for the heavyweight title rematch this summer after crossing the border to Poland, sources told ESPN.

The unified champion joined a territorial defense battalion in Kiev last month after Russia invaded Ukraine. During the war, Ukraine instituted martial law and banned men fit to serve aged 18 to 60. Usyk's longtime friend, Vasiliy Lomachenko, decided to remain in Ukraine and passed up the opportunity to fight George Kambosos for the undisputed lightweight championship on June 5 in Australia.

Usyk, however, will now head into a rematch with Joshua after he soundly defeated the Englishman via unanimous decision in September. Joshua, who entered the ring champion, exercised his contractual right to a rematch with financial terms already agreed upon.

The timing of the encore encounter was in doubt after Usyk, 35, told CNN earlier this month «I really don't know when I'm going to be stepping back in the ring.»

«My country and my honor are more important to me than a championship belt,» Usyk (19-0, 13 KOs) added.

Promoter Eddie Hearn of Matchroom Boxing told ESPN he planned to wait as long as Usyk needed. Hearn discussed the possibility of an interim fight for Joshua (24-2, 22 KOs), but now, plans are underway to secure a date and location for the rematch.

Usyk is ESPN's No. 2 heavyweight and No. 4 pound-for-pound boxer. The Olympic gold medalist won three heavyweight belts in just his third fight in the division following a dominant run at cruiserweight.

After the lopsided nature of the first meeting, Usyk will be installed as a heavy favorite to