US forces have not yet been ordered to pull out of Afghanistan despite President Donald Trump's plan to end involvement there, the commander of American forces in the Middle East, said on Thursday.

"We have not been directed to withdraw. There are no orders to withdraw anything," Central Command chief General Joseph Votel told the House Armed Services Committee.

"The political conditions of where we are in the reconciliation right now don't merit withdrawal," he said.

After 17 years, Trump wants to end US involvement in Afghanistan, where 14,000 American troops are still deployed.

Read more: Decision made for 'significant' troop withdrawal from Afghanistan: US official

But Votel said that despite some positive signs in talks between the United States and the Taliban forces, there has still not been enough progress.

One ongoing problem, he noted, is that the Taliban are still unwilling to negotiate directly with the Afghan government.

In addition, Afghan government troops are not yet ready to stand on their own, he said.

"These decisions have to be based more on conditions than specific times" and must "pivot off political progress".

"My advice is that any decision to reduce forces in Afghanistan should be done in full consultation with our coalition partners and of course the government of Afghanistan."

"The Afghan forces are dependent on the coalition support we provide for them," he added.

Warns of IS resurgence as 'caliphate' nears collapse

General Joseph Votel warned that the battle against the militant Islamic State (IS) group was "far from over" despite the group's loss of territory, as survivors abandoned the last shred of the group's collapsing "caliphate" in eastern Syria.

A fierce assault by US-backed forces has sparked an exodus of dust-covered children, veiled women dragging suitcases and dishevelled men, many of them wounded, from the village of Baghouz where besieged IS fighters are making a last stand.

But General Votel, head of the US Central Command, warned that many of those being evacuated are "unrepentant, unbroken and radicalised", calling for a "vigilant offensive" against the group.

The Syrian Democratic Forces (SDF) are waiting for more survivors to leave before dealing what they hope will be a final blow to IS fighters holed up in a makeshift camp along the banks of the Euphrates.

The SDF was not advancing Thursday out of concern for remaining civilians, but its fighters entered the settlement two days earlier and now control a chunk of it, an SDF source told AFP.

Remaining families have been pushed towards the far end of the camp near the river, he said.

Inside Baghouz on Thursday afternoon, an eerie quiet was interrupted by a brief burst of automatic gunfire.

AFP journalists taken into the battered hamlet watched the SDF stage a controlled explosion of a mine found on the side of a road during a sweep of the area.

Shortly after, a convoy of lorries carrying civilians and a handful of white vans carrying the wounded came trundling down the same street and out towards a screening point on the edge of village.

Hundreds of women disembarked at the outpost, where they waited to be processed and searched by the SDF and members of the US-led coalition.

'Unrepentant, unbroken and radicalised'

More than 7,000 people have exited the enclave over the past three days, mostly women and children.

The deluge of fire unleashed by SDF artillery and coalition air strikes at the weekend appears to have taken a toll on the diehard IS fighters still inside.

Votel, however, told Congress on Thursday that IS remains prepared for a resurgence, even though its territory is disappearing.

"Reduction of the physical caliphate is a monumental military accomplishment — but the fight against ISIS and violent extremism is far from over and our mission remains the same," he told Congress.

"The ISIS population being evacuated from the remaining vestiges of the caliphate largely remains unrepentant, unbroken and radicalised," he said.

"We will need to maintain a vigilant offensive against this now widely dispersed and disaggregated organisation."

US President Trump stunned allies in December when he announced all 2,000 US troops would withdraw from Syria as IS had been defeated.

The White House later said that around 200 American “peace-keeping” soldiers would remain in northern Syria indefinitely.

Members of Trump's administration, including the US Defence Department, have repeatedly warned that without a sustained presence, IS could resurge in Syria within months.

Symbolic victory

Around a tenth of the nearly 58,000 people who have fled the last IS bastion since December were IS fighters trying to slip back into civilian life, according to the Syrian Observatory for Human Rights, a Britain-based war monitor.

IS fighters had previously managed to secure passage out of their former strongholds before US-backed forces recaptured the territory.

Remaining IS fighters, however, are now surrounded on all sides, with Syrian government forces and their allies on the west bank of the Euphrates blocking any escape across the river and Iraqi government forces preventing them from moving downstream.

A senior SDF officer said 400 IS fighters were captured on Tuesday night as they attempted to slip out of Baghouz and reach remote hideouts.

The battle against IS is now the main front in the Syrian war, which has claimed more than 360,000 lives since 2011.

The capture of Baghouz would mark the end of IS territorial control in the region, where its "caliphate" proclaimed in 2014 once covered huge swathes of Syria and Iraq.

At its peak, the proto-state was the size of the United Kingdom and administered millions of people.

It effectively collapsed in 2017 when IS lost most of its major cities in both countries in the face of multiple offensives.

But despite the impending loss of Baghouz, which the SDF says is only days away, the group continues to carry out deadly attacks in Syria and Iraq.