The U.S. Army general picked to lead U.S. and NATO forces in Afghanistan warns the security situation there is deteriorating despite a valiant effort by Afghan forces.

Lieutenant-General John "Mick" Nicholson told the Senate Armed Services Committee on Thursday that terror groups like Islamic State and al-Qaida continue to see Afghanistan as an attractive sanctuary. He warned the U.S. may need to take a more aggressive approach.

"We still see attempts by terrorist organizations to get into Afghanistan," Nicholson said. "Do we have the right level of CT [counterterrorism] capability to deal with that?"

Of particular concern to U.S. military and intelligence officials is the spread of the Islamic State group, which has sought to establish a sanctuary in Nangarhar province, and a resurgent al-Qaida in Kandahar province.

The Taliban have also re-emerged as a threat, briefly seizing the northern city of Kunduz last year while also taking key districts in Helmand province. There are concerns, too, that the Taliban have hopes of retaking their spiritual home in Kandahar.

Nicholson assured lawmakers he would not let the U.S. sit idly by.

"We need to prevent Kandahar from falling into the hands of the Taliban," Nicholson said, adding he would "absolutely" recommend using U.S. military force to prevent the Taliban from retaking the provincial capital.

If approved by lawmakers, Nicholson would take over as the commander for U.S. and NATO forces in Afghanistan from Gen. John Campbell, who is expected to retire.

‘Crisis situation’

The U.S. currently has about 9,800 troops in Afghanistan for counterterrorism activities and to train and advise Afghan security forces. But that number is expected to drop to about 5,500 by the end of the year, worrying lawmakers.

"I believe we are in a crisis situation," said Senate Armed Services Committee Chairman John McCain, a constant critic of the Obama administration's Afghanistan policy. "It makes no strategic or military sense to continue the withdrawal of American forces."

Republican Senator Kelly Ayotte also expressed alarm at the way the administration has telegraphed troop levels in Afghanistan to U.S. enemies.

"This has been a constant kabuki dance," Ayotte said. "We cannot afford to take on risks that allow obviously safe havens, again, for al-Qaida and ISIS engagement."

Nicholson said that, if confirmed, he would review U.S. troop levels during his first 90 days in command and make an appropriate recommendation, warning he saw the need for a long-term commitment.

Realistic expectations needed

But he also said the U.S. needed to have a realistic expectation of what can be achieved.

"This is Afghanistan. There will always be some level of violence in Afghanistan," Nicholson said.

"We're not trying to create a Western-style society here," he added. "We are looking at an adequate level of security to prevent the re-emergence of transnational terrorist threats."

Nicholson is currently the commander of NATO's Allied Land Command, based at Izmir, Turkey. He has served several tours of duty in Afghanistan and also commanded the 82nd Airborne Division and a company in the Army's 75th Ranger Regiment.

Lawmakers praised Nicholson for his experience.

Nicholson's nomination could go before the full Senate for vote as early as next week.