Long-serving senior White House adviser Kellyanne Conway will “gratefully and humbly” leave the administration of US President Donald Trump at the end of August, citing the need to focus on her family.

In a statement issued on Sunday (US time), Ms Conway said she would “be transitioning from the White House at the end of this month”, citing a need to be at home with her four children after four years in the White House.

She also said she needed to help her children’s “remote learning during the coronavirus pandemic” as a reason to quit.

“Our four children are teens and ‘tweens starting a new academic year, in middle school and high school, remotely from home for at least a few months.

“As millions of parents nationwide know, kids ‘doing school from home’ requires a level of attention and vigilance that is as unusual as these times,” she wrote on Twitter.

Tweet from @KellyannePolls

Ms Conway, who was campaign manager during Mr Trump’s 2016 election run, will not be part of the stretch as Americans prepare to cast their votes in the presidential election on November 3.

Mr Trump is seeking a second term as President against Democratic challenger Joe Biden.

Her husband George Conway, a lawyer who renounced Mr Trump after the 2016 election, has also reportedly removed himself from Twitter and from the Lincoln Project, a group of Republicans devoted to defeating Mr Trump.

Ms Conway on the campaign trail in 2016. Photo: Getty

The politically adversarial marriage generated much speculation in political circles and online.

“We disagree about plenty but we are united on what matters most: the kids,” Ms Conway wrote.

“This is completely my choice and my voice. In time, I will announce future plans. For now, and for my beloved children, it will be less drama, more mama.”

The Associated Press reported Ms Conway, a trusted and loyal confidante who had outlasted dozens of Mr Trump’s senior staff, delivered the news in the Oval Office at the weekend. She said her job had been “heady” and “humbling”.

She is still slated to speak at the Republican National Convention this week.

A 2017 shot of Kellyanne Conway with her daughters also captured a throwback photo of Conway. Photo: AAP

Ms Conway worked for years as a Republican pollster and operative and originally supported senator Ted Cruz in the 2016 Republican primary. She moved over to the Trump campaign and that August became campaign manager as Stephen Bannon became campaign chairman.

Mr Bannon, who is no longer with Mr Trump’s administration is on bail after being charged with fraud on August 22.

Ms Conway was known for her robust defence of the President in media appearances, at times delivering dizzying rebuttals while once extolling the virtues of “alternative facts” to support her case. She has been informal adviser to Mr Trump’s re-election effort but has resisted moving over to the campaign.

Her departure comes at an inopportune time for Mr Trump, who is behind in the polls as the Republican National Convention begins on Monday.

-with AAP