The number of British troops in Afghanistan could be substantially increased in further attempts to fight the Taliban.
Defence Secretary Gavin Williamson has written to the prime minister advising the boost in soldiers, though the decision is yet to be finalised.
There are already 600 soldiers on the ground in Afghanistan, with between 400 and 450 additional troops suggested to join them.
This follows pressure from US President Donald Trump as he appealed for for international allies to do more to support Afghan forces.
The Ministry of Defence has said the UK's contribution to the mission against the Taliban has been kept "under constant review".
President Trump has increased US presence in Afghanistan after unveiling his strategy for South Asia last August.
4,000 troops are thought to have been deployed to support the 8,400 already on the ground in a bid to prevent a Taliban takeover, assist in training Afghan forces and target ISIS and al Qaida militants.
According to recent intelligence analysis shared with ITV News, Islamic State's presence on the Afghanistan-Pakistan border has increased by 20% in just a year.
This is despite a major Afghan-US operation involving the so-called 'Mother Of All Bombs', America's most powerful non-nuclear explosive.
Former general Sir Richard Barrons has warned that even more troops could be required, and they should be prepared to accompany Afghan forces on operations.
The retired officer said the decision to end combat operations in Afghanistan at the end of 2014 “hasn’t worked”.
Speaking to BBC Radio 4’s Today, he said that 400 extra troops would “send an important message to our allies,” and that more should be done to signal to the Taliban that “they will never bring this fight in Afghanistan to an end by fighting, they have to resort to dialogue”.
But he suggested a greater military presence and an enhanced – and more dangerous – role should be considered, with troops leaving the relative safety of their bases to accompany Afghan forces on operations.
“I absolutely think, if we are going to make a meaningful contribution, we will have to find the courage to train, advise, assist and accompany them into action,” General Barrons said.
“With that comes some risks and consequences, but that’s how you make a difference.”
General Barrons also suggested that the UK should deploy around 10% of the troops sent by the US, which would lift the British contribution to more than 1,200.
A Ministry of Defence spokesman said: “The support the UK provides Afghanistan on security, development and governance is crucial to building a stable state and reducing the terrorist threat to the UK.
“We remain committed to Nato’s non-combat Resolute Support mission, in which we play an important role, and keep our contribution under constant review.”
On Thursday, US State Department spokeswoman Heather Nauert said secretary of state Mike Pompeo had “reinforced our enduring investment in Afghanistan” in a conversation with the country’s president, Ashraf Ghani.
The reported change in approach is said to come amid concerns over how Mr Trump will approach a coming meeting of Nato leaders.
Theresa May is expected to join the president at the summit in Brussels in July, with Mr Trump then set to make a visit to the UK.
Mr Trump has repeatedly called for Nato members to meet their defence spending commitment of 2% of gross domestic product (GDP) and has threatened to walk away from the organisation if his demands are not met.
During a meeting with Mr Trump in Washington on Thursday, Nato general secretary Jens Stoltenberg said all members have increased their spending, in part due to Mr Trump’s approach.
After the talks Mr Stoltenberg said it is “very important that we all contribute more to our shared security”.