Former National Basketball Association (NBA) player Dennis Rodman said on Aug. 20 that he plans to travel to Russia to attempt to secure the release of fellow basketball star Brittney Griner.

"I got permission to go to Russia to help that girl," Rodman told NBC News, adding that he is "trying to go this week."

Rodman did not specify who had given him permission to travel to Russia.

Rodman does not need special permission from the United States to travel to Russia. However, the U.S. State Department has issued a travel advisory that strongly discourages U.S. citizens from entering Russia.

A Russian court sentenced Griner to nine years in prison for drug possession earlier this month. While her lawyers have filed an appeal, it is understood that there are separate talks underway for a prisoner swap to bring Griner back to the U.S.

Rodman has expressed confidence in his understanding of Russian President Vladimir Putin, saying the knows the leader "too well."

In 2014, Putin invited Rodman to a trip to Moscow and Rodman described the leader as "cool."

If Rodman travels to Russia, it will not be the first time he has conducted informal diplomacy with an international leader who has tense relations with the U.S.

Describing himself as a "basketball ambassador," Rodman has a friendship with North Korean leader Kim Jong-un and has credited himself with helping to secure the release of American Kenneth Bae from North Korea.

Rodman has won five NBA titles and was inducted into the NBA hall of fame.