Suhail Shaheen told British news station Sky News that the date is “a red line,” despite recent noises from the Biden administration that suggest the U.S. is considering staying longer if doing so is required to complete the Kabul airlift operation.

“President Biden announced that on 31 August they would withdraw all their military forces. So if they extend it that means they are extending occupation while there is no need for that,” Shaheen told correspondent Sally Lockwood.

“If the U.S. or U.K. were to seek additional time to continue evacuations, the answer is no. Or there would be consequences. It will create mistrust between us. If they are intent on continuing the occupation it will provoke a reaction.”

It comes after Defense Secretary Lloyd Austin said that as the deadline for ending the evacuation approaches, he will make a recommendation to the president about whether to give it more time.

“We’re gonna continue to assess the situation and again, work as hard as we can to get as many people out as possible and as we approach that deadline, we’ll make a recommendation to the president,” he told ABC’s This Week.

In remarks at the White House on Sunday, President Joe Biden did not rule out an extension of the deadline he set before the Taliban’s swift takeover of the country earlier this month.

The U.S. has evacuated and facilitated the evacuation of about 30,300 people on military and coalition flights since August 14, a White House official told the Associated Press, but tens of thousands of people are still waiting to join the airlift from Kabul.

Biden said that discussions with the military are underway on potentially extending the airlift beyond August 31. “Our hope is we will not have to extend, but there are going to be discussions, I suspect, on how far along we are in the process.”

The president has repeatedly defended his decision to end America’s longest war and maintained that getting all Americans out of the country would have been challenging no matter the circumstances.

“The evacuation of thousands of people from Kabul is going to be hard and painful, no matter when it started, when we began,” the president said. “It would have been true if we’d started a month ago, or a month from now. There is no way to evacuate this many people without pain and loss of heartbreaking images you see on television.”