The top American commander in Afghanistan said Thursday that he wants "greater flexibility" to potentially keep more U.S. troops there than are called for under the drawdown plan President Obama outlined last year.

"I have provided options on adjusting our force posture through my chain of command," Army Gen. John Campbell told lawmakers during his first testimony on Capitol Hill in seven months.

Campbell signaled that he wants to change current plans that call for keeping 10,000 U.S. troops in Afghanistan this year, dropping to about 5,000 for 2016 and then bringing an end to the military mission shortly before Obama leaves office in January 2017.

Campbell said his views are influenced in part by Afghan President Ashraf Ghani's request for more U.S. support for Afghan forces in areas including logistics, intelligence and air support.

"I think I provide some options, both for President Ghani and for my senior leadership here, to take a look at what would allow us the flexibility to continue to get after the [train-advise-and-assist] mission and the [counterterrorism] mission," Campbell said.

One senator asked Campbell whether he agreed with some retired officers who say the U.S. force level in Afghanistan should be closer to 20,000.

"Sir, none of the options recommend an increase like that," Campbell said. "Most of the options I'm discussing with my senior leadership include allowing more flexibility on glide slope, allowing more flexibility on locations."

Campbell suggested he is concerned about one aspect of the current drawdown plan that calls for ending U.S. military operations outside Kabul later this year.

"The issue is how long we stay engaged at the regional level in the transition year of 2015," he said.

Campbell downplayed new reports that the Islamic State group, sometimes referred to as Daesh or ISIL, is gaining a foothold in Afghanistan or forging an alliance with Afghanistan-based Taliban militants.

"The possible rise of Daesh, or ISIL, is also a new development. Thus far we believe that the nascent Daesh presence in Afghanistan represents more of a rebranding of a few marginalized Taliban, but we're still taking this potential threat, with its dangerous rhetoric and ideology, very, very seriously," Campbell said.

"We're all driven to prevent Daesh from establishing a meaningful foothold in Central Asia."

Obama already has revised his drawdown plan once. Last year he initially said U.S. force levels in Afghanistan would fall to 9,800 by the end of 2014. But late in the year he authorized several hundred additional troops, keeping end strength above 10,000 into this year.

Obama is facing pressure to ratchet up his commitment to Afghanistan for several reasons.

The rise of the Islamic State group in Iraq last year raised new questions in hindsight about the White House and Pentagon decision against keeping U.S. troops there for an advise-and-assist mission after 2011. Scattered reports of Afghan insurgents claiming allegiance to IS fuel those concerns.

Politically, hawkish views are more dominant on Capitol Hill since the Republicans took control of the Senate in January. Sen. Jeff Sessions, a R-Ala., said Thursday he believes that the "rate of withdrawal is too high, too steep in Afghanistan."

"I believe our Congress, in a bipartisan way, is open to having a more robust assistance to the Afghan forces. I feel that in talking to my colleagues on both sides of the aisle, I think the American people are willing to stay the course and help, not in an out-front way but in a supportive way — more than a lot of people think, if we articulate that," Sessions told Campbell.

"I believe it's important for the president to articulate that," Sessions said.

Campbell said, "Afghanistan continues to be a dangerous place" and noted that the casualty rates for the Afghan forces were up 5 percent to 7 percent last year.

"However, this must be viewed in light of the fact that their operational tempo was four times greater in 2014 than it was in 2013 and that over 100,000 coalition forces were no longer on the battlefield," he said, adding that casualty and attrition rates for the Afghan forces "have not impacted combat readiness too severely."

Campbell described Kabul as "the fifth fastest-growing city in the world," and showed lawmakers statistics about the rise in literacy rates, roadway construction, cellphone use and girls attending school.

Life expectancy has risen from 43 years in 2001 to 64 years today, he said.