WASHINGTON: As it intensifies its withdrawal from Afghanistan, the U.S. military is being forced to fly massive amounts of gear and equipment out of the country instead of using cheaper overland and sea routes, according to Pentagon officials.

Military logisticians would like to send home 60 percent of their equipment and vehicles by trucking them into Pakistan and then loading them onto ships — the least expensive method by far. But cargo is flowing out on that route at only one-third the planned rate, the officials said.

Officials declined to elaborate on the reasons for their heavy reliance on the more expensive methods of transport. They said, however, that Deputy Defense Secretary Ashton B. Carter and other Pentagon officials are scheduled to arrive Friday in Kabul to meet with senior Afghan officials on the issue. Carter will also meet with U.S. troops before touring other countries in the region.

The government of Afghanistan closed the border this summer after a dispute over whether the Pentagon and its contractors should have to pay $70 million in customs “fines” for taking the military gear out of the country. The Pentagon has refused to pay, calling the penalties a thinly veiled attempt at a shakedown.

U.S. and Afghan officials said last month that they had resolved the conflict, after the government in Kabul reluctantly backed down and reopened the border crossings into Pakistan.

“This issue is over for us. The problem has been settled,” said Najibullah Manelai, a spokesman for the Afghan Finance Ministry. “We have said enough about it already, and we are not willing to talk about it anymore.”

The U.S. military withdrawal from Afghanistan poses an enormous logistical challenge. The landlocked country is halfway around the world, has few rail lines and poor roads, and is ringed by mountainous terrain. By the end of next year, U.S. officials say, they need to pull out 24,000 vehicles and 20,000 shipping containers, one way or another.

The Pentagon has budgeted $5 billion to $7 billion to ship all that gear home. But the final tab will hinge greatly on the extent to which the military can rely on the ground routes through Pakistan.

The primary alternative is to load the equipment on cargo planes and fly it out — either all the way back to the United States, or to seaports in the Persian Gulf and the Arabian Sea. But those options are three to seven times as expensive as the route through Pakistan.

Another alternative is to ship cargo by rail or truck across Afghanistan’s northern borders into Central Asia and Russia. But the Defense Department, after working for years to secure transit agreements with those countries, expects to move only 1 or 2 percent of its equipment along those corridors, according to a senior defense official who spoke on the condition of anonymity under ground rules set by the Pentagon.

The northern land routes, though cheaper than air cargo, take the longest and are more expensive than the Pakistan option, the official said.

Finding a way to make full use of the Pakistan route has become an urgent priority because a bulge of equipment is scheduled to leave Afghanistan starting next month, the official said. Similar peaks of cargo traffic are planned for spring and in October 2014.

The United States has 60,000 troops in Afghanistan, but that number will dwindle to 34,000 by February. The U.S. and NATO combat mission is scheduled to end by December 2014. The Obama administration and Afghan leaders are still negotiating whether any U.S. troops will stay after that to help train Afghan security forces.

At the moment, the U.S. military is trucking about 20 percent of its gear via Pakistan, before loading it onto ships at the port of Karachi. The defense official said he was optimistic that traffic would pick up, but he acknowledged that the link was tenuous. “Every day, something can change,” he said.

Ammunition, weaponry and other sensitive materials must be transported by air for security reasons. About 28 percent of cargo is being flown all the way back to the United States, and 50 percent is flown to seaports in the Middle East, then loaded onto ships for the remainder of the journey.

“The more we put on the [Pakistan route], hopefully the more money all of us will have in our pockets,” the defense official said. “It’s cheaper and just as effective if it’s working.”