The Prime Minister will make a statement to the House of Commons on Monday when Parliament returns from its summer recess to confront a potential humanitarian disaster in the making.
Mr Johnson and Foreign Secretary Dominic Raab have both been subject to criticism over the withdrawal of foreign forces from Afghanistan and their response since the Taliban takeover.
Thousands of Afghans who worked with Britain, their families and other vulnerable citizens are feared to have been left behind when UK troops departed Kabul last month.
And there have been warnings that the UK could face a heightened terror threat if extremism is allowed to flourish once again in Afghanistan.
Speaking in the week marking the 20th anniversary of the 9/11 attacks that prompted the US and its allies to go to war in the nation, Mr Johnson will vow to "use every economic, political and diplomatic lever to protect our country from harm and help the Afghan people".
The Prime Minister is also expected to update MPs on the new resettlement programme for Afghans to come to the UK in the coming years.
No 10 said he will announce an additional £5 million to help military charities offering support on mental health issues to veterans with the aim of ensuring "no veteran's request for help will go unanswered".