Eccentric former NBA star Dennis Rodman is planning a trip to Russia in an effort to seek the release of imprisoned WNBA player Brittney Griner, NBC News reported on Sunday.

The network quoted Rodman as saying that he was hoping to fly to Russia this week in an attempt to help basketball superstar Griner, who was sentenced to nine years in jail by a Moscow court earlier this month on a drug charge.

"I got permission to go to Russia to help that girl," Rodman told NBC. "I'm trying to go this week."

No further details were provided by Rodman, who was speaking at a restaurant in Washington where he was attending a sports apparel convention, according to NBC.

A senior official for US President Joe Biden's administration said in a statement to AFP, "it is public information that the Administration has made a significant offer to the Russians and anything other than negotiating further through the established channel is likely to complicate and hinder release efforts."

Rodman, 61, a five-time former NBA champion, has a record of unorthodox forays into geopolitics.

He has formed a relationship with North Korean leader Kim Jong-Un over the past decade, and has made several trips to the reclusive state. He traveled to Singapore in 2018 when Kim famously met former US President Donald Trump.

Rodman has also spoken approvingly of Russian President Vladimir Putin in the past. In 2014 he described Putin as "actually cool" after meeting the Russian leader in Moscow.

Two-time Olympic basketball gold medalist and Women's NBA champion Griner was arrested at a Moscow airport in February for possessing vape cartridges with a small amount of cannabis oil.

The 31-year-old, who was in Russia to play for the professional Yekaterinburg team during her off-season from the Phoenix Mercury, was charged with smuggling narcotics and was sentenced to nine years in a penal colony in early August.

Griner pleaded guilty to the charges, but said she did not intend to use the banned substance in Russia.

Since her arrest, Moscow and Washington have been in talks about a potential prisoner exchange, despite soaring tensions over Russia's military intervention in Ukraine.