Russia probe picks up

US President Donald Trump added a top impeachment attorney to his legal team Wednesday after the lead White House lawyer for the Russia meddling investigation stepped down.

The recruitment of Emmet Flood, who represented president Bill Clinton when he was impeached by the House of Representatives and tried by the Senate in 1998-99, signaled that the White House is going on the offensive as it girds for a tough battle over presidential powers and possibly obstruction allegations with Special Counsel Robert Mueller, who leads the Russia probe.

"Emmet Flood will be joining the White House Staff to represent the president and the administration against the Russia witch hunt," Trump's Press Secretary Sarah Sanders said.

Flood joined the team as Ty Cobb, who had urged the president to be more conciliatory with Mueller, stepped down from his role managing White House relations with the year-old investigation.

Both Cobb and John Dowd, who quit the president's legal team in March, were reportedly displeased that Trump was not following their advice in the case, especially with his repeated attacks on Mueller.

The changes come as the White House is under increasing pressure from the probe.

Mueller is investigating whether the Trump campaign colluded with Russia during the 2016 election, as well as possible obstruction of justice by Trump.

The investigation has already yielded 19 indictments, including of three top campaign aides and advisors. If obstruction or other charges are ultimately levelled against the president, it could possibly lead to his impeachment.

Belying their concerns, Trump and Republicans in Congress have threatened to remove Mueller and other senior Justice officials, a move that top members of Congress have also warned could result in Trump's impeachment.