Mueller probing Trump's attacks on Jeff Sessions

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 US 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.

Meanwhile, Trump's former campaign manager Paul Manafort pleaded not guilty on Wednesday to a new indictment brought against him in the investigation into alleged Russian meddling in the 2016 election and will face trial in September.

Manafort's former business partner Rick Gates, another Trump ex-campaign official, decided last week to cooperate with the investigation.

Manafort is facing two separate indictments on an array of charges, including conspiracy to launder money, filing false tax returns, bank fraud, and failing to register as a foreign agent despite lobbying in the United States for the pro-Kremlin Ukrainian government.