The U.S.-led coalition has launched a new offensive against one of Afghanistan's most virulent militant networks and plans to ramp up operations next year along the eastern border with Pakistan before the American troop drawdown gathers steam, the top commander said Wednesday.

Marine Gen. John Allen told The Associated Press that the "high-intensity, sensitive" operation that began just a few days ago targets the Haqqani group, a Pakistan-based militant network that attacks Afghan and coalition forces. The U.S. has been urging the Pakistanis incessantly to clamp down on Haqqani fighters, who have ties to both the Taliban and al-Qaida and have been blamed for most of the high-profile attacks in the heart of the Afghan capital, Kabul.

Allen would not discuss details of the operation, saying only: "Every now and again, one of these organizations that has been able to manifest itself on this side of the border is going to have to get some special attention, and that's what's happening now."

In a wide-ranging interview, Allen also told the AP that the process of handing off security to Afghan forces was going to move faster than initially planned. Afghan President Hamid Karzai wants the Afghan army and police to be in the lead in protecting and defending the nation by the end of 2014.

Allen commands more than 130,000 international troops in Afghanistan, including about 98,000 from the United States.

Most of the coalition forces are deployed in southern Afghanistan, where they have had success in routing insurgents from their strongholds to make room for the international community and Afghan government to improve governance and services. If the coalition, with the help from the Afghan forces, can hold areas in the south, some coalition forces, perhaps a few 1,000-member battalions, could be moved to the east, Allen said.

"The intent in the east is to secure the province of Kabul and the approaches to the city," Allen said. "What I want to do is to expand that security zone around Kabul, which is going to require more forces" in the east.

He said most of the first 10,000 American troops to be withdrawn by the end of the year will come from support units, but roughly one-third will be combat forces. The combat forces will be taken mostly out of the west and north _ not the hotspot areas in southern and eastern Afghanistan.

The 10,000 troops in the first drawdown include two National Guard reserve units; one Army infantry battalion from an area yet to be determined; one Marine infantry battalion deployed in the south; and military personnel working in headquarters operations and support units. The U.S. is thinning forces by moving tasks back to the United States, handing them off to civilian contractors, eliminating jobs or making one person do the work of two, he said.

To satisfy President Barack Obama's mandate to withdraw another 23,000 U.S. forces by Sept. 30 of next year, many more combat units will be tapped to leave, he said in his office in the heavily fortified coalition headquarters in Kabul.

The fit four-star general in his 50s, who succeeded retired Gen. David Petraeus in July, came to Afghanistan as the international military coalition prepares to withdraw fighting forces by the end of 2014, leaving foreign troops in support or training roles only.

This summer, Afghan forces began taking charge of security in seven areas of the country, the first in what was to be a six-step transition process.

Allen said the plan is now for the transition to be achieved in five steps _ the last starting as early as the fall of 2013 instead of late 2013 or early 2014 as had been discussed.

Initially, the idea was to have Afghan security forces take charge in the most peaceful areas first, he said. Afghan and coalition officials and others, however, recently decided that it would be unwise to transfer the most volatile provinces in 2014, especially when the international force's footprint will be shrinking.

U.S. Ambassador Ryan Crocker echoed Allen's comment on Sunday during a trip to the western city of Herat _ a provincial capital in the first group of areas to start transition.

"The original logic was you go from easy to hard," he told the AP. "But since you're going from a lot of troops to fewer troops, there is also a pretty good case to be made for transitioning the hard areas while you've got the heavy, ready reserve" on the ground.