KABUL — America will not accelerate the removal of its troops from Afghanistan despite a series of attacks on U.S. soldiers by Afghan security personnel angered over the burning of Qurans at a coalition airfield, according to the top U.S. diplomat here.

Ryan Crocker, the American ambassador to Afghanistan, emphasized in an interview at the U.S. Embassy in Kabul that the troop withdrawal would proceed as outlined last summer by President Barack Obama.

“We have not invested the billions of dollars we have and the lives of 1,900 Americans to see the Taliban retake this country and al-Qaida once again be able to restage here,” Crocker said.

“That’s why we’re here — to be sure al-Qaida is defeated and that Afghanistan is never again a safe haven for forces that would seek to attack us on our own soil.”

There are 90,000 U.S. troops deployed in Afghanistan. The number will be reduced to 68,000 by Sept. 30, and most of the remaining troops will leave by the end of 2014.

Crocker’s statements echoed those of Obama and Secretary of Defense Leon Panetta this week as top U.S. officials attempt to counter deepening suspicion between Afghans and coalition forces, and mounting criticism in America of a war more than a decade old.

Since Feb. 21, when reports surfaced that soldiers at Bagram Airfield had burned several copies of the Quran, Afghan security forces have shot and killed six U.S. servicemembers in three separate incidents.

The latest shooting occurred Thursday, when two Afghan soldiers and a literacy instructor opened fire at a base in Kandahar province, killing two U.S. soldiers and wounding a third. Coalition troops returned fire and killed the two Afghan soldiers.

The attack followed the shooting deaths of a pair of American soldiers by an Afghan counterpart at a base in Nangarhar province on Feb. 23.

Two days later, an Afghan police officer gunned down two U.S. military advisers at the Interior Ministry building in Kabul. The suspect remains at large.

The slayings at the ministry led U.S. Marine Gen. John Allen, NATO’s commander in Afghanistan, to recall the hundreds of U.S. advisers who work in government buildings in the capital.

Some advisers have since returned to their offices. But the succession of what the military terms “green-on-blue” attacks could strain the relationship between Afghan security forces and the coalition troops charged with training them before departing in 2014.

Crocker, while describing the killings as “horrible incidents,” sought to place the attacks in the larger framework of the ongoing effort to build an Afghan military force of 350,000 troops.

“When you look at the number of international advisers out there every day with Afghan forces, both in training and in an operational context, you’re talking about a tragic but very, very tiny percentage of incidents,” he said.

RAMSTEIN AIR BASE, Germany — U.S. Air Forces in Europe celebrated 60 years of the U.S. Air Force in Rhineland-Pfalz on Friday at Ramstein Air Base.

A ceremony was held in a massive double bay hangar on the flight line of the air base with a formation of several squadrons and groups representing the 86th Airlift Wing in service dress uniforms.

German residents from the area, civic and military leaders also attended the celebration.

Among those speaking were Gen. Mark A. Welsh III, USAFE commander; Kurt Beck, minister president of Rhineland-Pfalz; Brig. Gen. Charles K. Hyde, commander of the 86th Airlift Wing and U.S. Ambassador Philip D. Murphy.

“There is hardly a German citizen who does not have an American neighbor, tenant or co-worker,” Hyde said. “Personal relationships between Germans and Americans span decades and are where the friendships we experience today have their roots.”

“Citizens of Rhineland-Pfalz, thank you for hosting the U.S. Air Force. Our airmen and the thousands of families which call you friends and neighbors and your villages home, thank you.”