KABUL, Afghanistan — The ongoing Taliban offensive in Afghanistan demands a reassessment of the Obama administration's current plan to drawdown U.S. forces, U.S. Sen. John McCain said Saturday during a visit to the country's capital.

The Republican told reporters that Afghan national forces are fighting bravely, but suffering heavy losses in the field.

American and international troops have already stopped playing a combat role, remaining as trainers for local forces. The international numbers will be reduced further at the end of 2016. But McCain said reductions should be based on conditions on the ground.

"With the rise of ISIS and the distinct fighting season that is marked this year, the threat environment continues to evolve in ways that clearly, in my view, demands a reassessment of the administration's current calendar-driven drawdown of U.S. forces with a plan that must be based on conditions on the ground," McCain said.

Afghan forces have struggled to fight off the Taliban since the U.S. and NATO combat mission officially concluded at the end of last year. More than 2,300 Afghan soldiers, police and pro-government fighters have been killed since the start of the year — more than the total number of U.S. troops killed since the 2001 invasion that ended Taliban rule.

Meanwhile, Afghan lawmakers rejected President Ashraf Ghani's nominee for defense minister, a position that has remained empty for more than nine months amid some of the toughest fighting since the Taliban insurgency began 14 years ago. Masoom Stanekzai received 84 out of the 107 votes needed for parliamentary approval.

Stanekzai's rejection reflects in part a power struggle between Ghani and Afghanistan's Chief Executive Abdullah Abdullah. Stanekzai, the second nominee put forth by Ghani to be rejected, is also seen by some to be ineffective, based on the chaotic security situation around the country.

Stanekzai previously led the High Peace Council negotiating body charged with ending the conflict with the Taliban. He has been serving as the country's top defense official in an acting capacity.

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In January, Gen. Sher Mohammad Karimi also failed to get enough votes in parliament. It could be months before a new nominee for the position is put forth.

Also Saturday, men on a motorcycle attacked a pair of schoolgirls in the western city of Herat, throwing an unknown chemical substance in their faces, authorities said. The victims, aged 16 and 17, were hospitalized in stable condition, said Mohammad Rafiq Sherzai, spokesman for the Herat hospital.

It was not clear what sort of substance was used in the attack but it was not acid, he added.

Police were searching for the two men, who attacked the students as they were on their way to school, and no arrests had been made, said Rauf Ahmadi, spokesman for the Herat police.

Authorities on Saturday also raised the death toll from a Taliban attack on several police checkpoints in Wardak province. The Wednesday night attack left 24 police dead, up from the previously reported total of seven, and two wounded, according to a statement from the provincial governor's office.

Authorities have regained control of the checkpoints, which had been overrun by Taliban fighters. Forty insurgents were killed and 18 wounded, the statement said.