US Deputy Attorney General Rod Rosenstein, who oversees the special counsel investigation into Russia's role in the 2016 presidential election, has verbally resigned in anticipation of being fired by President Donald Trump, Axios news site reported.

Rosenstein, the Number 2 Justice Department official, verbally resigned to White House Chief of Staff John Kelly, the report said, citing an unidentified source with knowledge of the matter.

A second source told Axios that Rosenstein is "expecting to be fired" so he plans to step down.

There was widespread speculation that Trump would fire Rosenstein after a New York Times report on Friday said in 2017 he had suggested secretly recording Trump and recruiting Cabinet members to invoke a constitutional amendment to remove him from the office.

The Times said none of those proposals came to fruition. Rosenstein denied the report as "inaccurate and factually incorrect."

MSBNC and CNN reported Rosenstein was summoned for a meeting at the White House today.

Rosenstein assumed the role in the Russia investigation after his boss, Attorney General Jeff Sessions, recused himself after his own contacts with Russia's ambassador to Washington while serving as a Trump campaign adviser became public.

Trump has regularly dismissed the investigation as a "witch hunt."