The special counsel in the Russia probe is investigating a period of time last summer when President Donald Trump seemed determined to push Attorney General Jeff Sessions to resign, the Washington Post reported on Wednesday.

Special Counsel Robert Mueller is looking into whether Trump's apparent effort to drive Sessions from his job was part of a pattern of attempted obstruction of justice, the Post said, citing people familiar with the matter.

Mueller's team, which is investigating alleged Russian meddling in the 2016 U.S. presidential election, has questioned witnesses about Trump's private comments in late July and early August, around the time he issued a series of tweets belittling Sessions, according to the Post.

Mueller is seeking to determine whether Trump's goal was to oust Sessions in order to pick a replacement who would exercise control over the investigation into possible coordination between Russia and the Trump campaign during the 2016 election, the Post said.

Russia has denied meddling in the campaign and Trump has denied any collusion took place.

The White House and the Justice Department did not immediately respond to requests for comment on the Post story.

Trump and Sessions have had a rocky relationship since Sessions recused himself a year ago from the Justice Department's Russia probe. The recusal paved the way for the appointment of Mueller, who has indicted several former Trump campaign aides and advisers.

On Wednesday, Trump skewered Sessions about his decision to order the Justice Department's inspector general to investigate allegations that the Federal Bureau of Investigation improperly obtained a warrant to conduct surveillance on a former Trump campaign adviser.

Trump said in a tweet that Session's decision not to use prosecutors to investigate the matter was "DISGRACEFUL."

Donald Trump tweet

Sessions, an early supporter of Trump's 2016 presidential campaign, responded with a terse statement in which he pledged "to discharge my duties with integrity and honor."