Militants set off a car bomb and used rocket-propelled grenades to storm the entrance of an airbase outside Jalalabad, near the Pakistani border Wednesday.
The Taliban say six suicide bombers killed dozens of Afghan and foreign forces in the brazen daylight attack. But NATO spokesman Brigadier General Josef Blotz refutes that claim.
"In this incident several insurgents were killed and I can tell you that the security perimeter was not breached and the insurgents were being stopped by Afghan and ISAF forces very effectively," Blotz said.
The attack appeared planned and coordinated, much like a Taliban assault last May on the Bagram air base, NATO's biggest in Afghanistan.
June has been the bloodiest month of the near nine-year-old war for foreign troops, with over 100 killed. The rising toll comes amid a troop surge for an operation that seeks to take on the Taliban in their heartland.
On Tuesday in Washington, U.S. General David Petraeus warned there are still difficult days ahead.
"My sense is that the tough fighting will continue, " he said. "Indeed, it may get more intense in the next few months. As we take away the enemy's safe havens and reduce the enemy's freedom of action, the Insurgents will fight back."
Petraeus has been nominated to head the U.S.-led war in Afghanistan after his predecessor, General Stanley McChrystal, resigned. McChrystal and his aides had made disparaging remarks about Obama administration officials in a magazine interview.
At Tuesday's Senate confirmation hearing, Petraeus said he believes the Afghan government and its international allies can still succeed in the fight against the Taliban.
But many observers say any progress will be slow. Jeremy Binnie, a terrorism and insurgency expert at IHS Jane's defense group, says instead of making sustainable gains and winning over the public, coalition troops have been preoccupied with chasing insurgents.
"What we're typically seeing that the coalition and Afghan allies are capable of securing sort of district centers, the center of these towns, and displacing the Taliban out of them," he says. "But the insurgents merely move a few miles down the road and they sort of set up a new safe haven and then they do their absolute utmost to undermine any perception of security."
Rampant corruption in the Afghan government is also raising doubts about the overall war strategy that is now aimed at winning the support of civilians and potential militant defectors.
U.S. Attorney General Eric Holder arrived in Kabul Wednesday to discuss the country's anti-corruption efforts. He also will discuss ways to improve Afghanistan's judicial system in his meetings with Afghan and U.S. officials.