Washington(CNN) President Donald Trump on Sunday said Afghanistan "can't be a laboratory for terror" as discussions over a potential US withdrawal from the country persist after nearly 20 years at war.

"Look we're there for one reason, we don't want that to be a laboratory ... It can't be a laboratory for terror. And we've stopped that we have a very, very good view," he told reporters on the tarmac before departing from New Jersey as he headed back to Washington.

Trump's comments come after he met with top national security advisers last week at his golf course in Bedminster, New Jersey, to review a US-Taliban peace plan that could end America's longest running war.

"We're looking at Afghanistan. We're talking to Afghanistan, both the government and also talking to the Taliban, having very good discussions. We'll see what happens ... We'll decide whether or not we'll be staying longer or not," he said.

Critics say it could trigger a surrender for the US and a betrayal of the Afghan government. Trump said Sunday the US government has had "very good discussions" with both with the Afghan government and with the Taliban but the President is far from trusting of the group.

"I'm not trusting anybody," Trump said. "It's a horrible situation that's going on in Afghanistan."

An omission

The peace plan is expected to formalize a significant withdrawal of US forces from Afghanistan -- from about 15,000 troops to 8,000 or 9,000 troops -- and enshrine official commitments by the Taliban to counterterrorism efforts in Afghanistan, according to the multiple sources familiar with the plan.

While the deal will include other elements, including a US-Taliban ceasefire, it also has at least one crucial omission: It is not expected to secure a commitment by the Taliban to hold its fire on the Afghan people or the Afghan military, according to sources familiar with the talks.

The Taliban do not recognize the Afghan government, which has not been involved in the talks the US has been holding with the Taliban in Qatar. While some minutiae of US special representative for Afghanistan reconcilliation Zalmay Khalilzad's agreement are still under discussion, sources say that the plan is 99% done.

The Taliban's insistence on only committing to a ceasefire with the US was a serious obstacle during the negotiations, a source close to the talks told CNN. US bilateral security agreements with the Afghan government mean they are obliged to assist their Afghan partners on the battlefield, which could complicate this agreement.

'A police force'

When asked about the reason behind keeping a US military presence in Afghanistan, Trump likened the American presence to "a police force."

"We're like a police force and that's about it, frankly. I think it's very important that we continue intelligence there in all cases because it is somewhat of a nest," he said. "If you look at what happened with the World Trade, essentially came out of Afghanistan, most of the people, I think they may not have come from Afghanistan originally but that's where they were taught."

The conflict has become America's longest-ever war and has ground into a stalemate, with neither side able to defeat the other and casualties rising among civilians as well as combatants.

Taliban attacks have not slowed down in recent years or months, even as the US has continued talks with the group.

Recent attacks

A suicide bomb attack at a wedding in Kabul on Saturday killed 63 people and wounded 182, an Afghan Interior Ministry spokesman said. Among the victims were women and children, spokesman Nasrat Rahimi said.

ISIS claimed responsibility for the attack. It said a Pakistani fighter detonated an explosive vest amid a large gathering of Shia Muslims, reported the SITE Intelligence Group, which monitors terrorist group activities. The terror group also said a car bombing followed the initial attack, added SITE.

On August 7, the Taliban claimed responsibility for a suicide attack in which an explosive-laden vehicle targeted Afghan security forces in Kabul, killing 14 people and wounding 145, mostly women, children and civilians.

The Taliban has also claimed responsibility for many of the more than 1,500 civilians killed or wounded in the country in July, the highest monthly toll in over two years, according to the UN Assistance Mission in Afghanistan. In 2018, there were almost 4,000 civilian deaths in Afghanistan, according to a UN report, the highest recorded number in the war.

What's next

Trump also teased more information could be forthcoming, saying "some things are going to be announced over the next couple of weeks as to what happened, who has been taken out, a lot of people have been taken out that are very bad, both ISIS and al-Qaeda."

When asked about recent criticism of a possible pullout of Afghanistan by Sen. Lindsey Graham, normally a staunch supporter of the President, Trump responded, "Well, I guess that means Lindsey is a tough man, OK?"