Biden announced plans last month to withdraw the remaining 2,500 troops from Afghanistan, where the U.S. has been at war for nearly 20 years. All U.S. troops are expected to leave the country by Sept. 11.
As the U.S. begins its withdrawal, the former secretary of state was asked by CNN about Biden's decision to leave.
"Well, it's been made. And I know it is a very difficult decision," Clinton told the network on Sunday. "This is what we call a wicked problem. You know there are consequences both foreseen and unintended of staying and of leaving. The president has made the decision to leave."
Clinton noted the potential of "two huge consequences," that the U.S. government should focus on. She said there is the potential collapse of Kabul and the takeover by the Taliban and the resumption of global terrorist activities.
"I think these two huge sets of issues have got to be addressed," she said. "I mean it's one thing to pull out troops that have been supporting security in Afganistan, supporting the Afgan military, leaving it pretty much to fend for itself. But we can't afford to walk away from the consequences of that decision."
Clinton and former Secretary of State Condoleezza Rice previously told members of the House Foreign Affairs Committee they were worried about Biden's plan to withdraw all U.S. troops from Afghanistan, according to Axios.
The U.S. and its NATO allies went into Afghanistan together on Oct. 7, 2001, to hunt the Al Qaeda perpetrators of the 9/11 terrorist attacks who lived under the protection of the country's Taliban rulers. In his withdrawal announcement, Biden said the initial mission was accomplished a decade ago when U.S. Navy SEALS killed Usama bin Laden in his hideout in neighboring Pakistan.
The U.S. is estimated to have spent $2 trillion in Afghanistan alone over the last 20 years, losing over 2,300 American soldiers during the fighting that ensued, along with an estimated over 47,000 Taliban and Afghan civilians, according to the Costs of War project.
In a statement by the White House on Sunday, the president said Al Qaeda's presence in Afghanistan was "greatly degraded."
U.S. Secretary of State Antony Blinken told CBS' "60 Minutes" in an interview that aired Sunday night that Washington has to be prepared for every scenario.
"Just because our troops are coming home doesn't mean we're leaving," he said. "We're not. Our embassy's staying, the support that we're giving to Afghanistan when it comes to – economic support, development, humanitarian, that – that remains. And not only from us, from partners and allies."
The Associated Press contributed to this report