In a move signaling a major escalation in the offensive against the Taliban, the U.S. military is deploying heavily armored battle tanks to Afghanistan for the first time in the nine-year war.

The company of M1 Abrams tanks, each weighing in at 68 tons and propelled by jet engine, are equipped with 120mm guns that can destroy a house from more than a mile away.

"The tanks bring awe, shock and firepower," an officer familiar with the tanks told the Post. "It's pretty significant."

The tanks will initially be used by Marines engaged in an intense firefight with Taliban cells in the country's southwest province of Helmand, the newspaper said, giving American ground forces the power to target insurgents with a longer range and more lethal punch than from any other U.S. military vehicle.

The added artillery comes amid the fiercest coalition operation against the Taliban since fighting began in 2001, several NATO commanders told the Post. In October alone, U.S. and NATO aircraft unleashed more than 1,000 bombs and missiles on insurgents -- more than any single month since the war began.

"We've taken the gloves off, and it has had huge impact," one senior official told the paper.

Meanwhile, the Defense Department said Thursday Afghans may not be ready to assume full responsibility for security in their country by the target date of 2014 and some U.S. forces may need to remain beyond that date.

Pentagon press secretary Geoff Morrell called the date "an aspirational goal" and not a deadline either for full Afghan control or complete U.S. military withdrawal.

President Barack Obama and other NATO leaders are expected to endorse the 2014 timeline proposed by Afghan President Hamid Karzai when the alliance meets at a summit this weekend. The goal is expected to allow for a gradual drawdown of 150,000 international forces over the next four years. Roughly 100,000 of those are American.

"The goal is to have Afghan security forces in the lead over the preponderance of the country," by the end of 2014, but those forces might not have the lead role everywhere, Morrell said.

"That would be the hope, that's what we would shoot for," Morrell said.

"It does not mean that all U.S. or coalition forces would necessarily be gone by that date. There may very well be the need for forces to remain in country albeit hopefully in smaller numbers."

The 2014 date provides a horizon for a war now in its 10th year that is deeply unpopular in Europe and the United States and helps Karzai reassure Afghans that he has not agreed to a permanent U.S. occupation.

Even staying until 2014 is something of a hard sell for some NATO allies and few would be likely to remain in Afghanistan in large numbers after that. Britain, which has the second-largest number of forces in Afghanistan, has pledged to bring almost all of those 10,000 forces home by 2015.

The Associated Press contributed to this report.