Pentagon press secretary Geoff Morrell said Defense Secretary Robert Gates will receive a proposal Friday to send additional Marines to southern Afghanistan where NATO forces have faced a growing Taliban resurgence for a "one-time, seven-month deployment."
If the deployment is approved, it would raise the number of American service members in Afghanistan to about 30,000.
The move highlights divisions between Western allies over how many troops to commit to the country. Washington, stretched by last year's troop surge in Iraq, has for months been trying in vain to persuade NATO allies to send more combat troops to Afghanistan, Reuters reported.
European governments have been reluctant to increase their operations and, wary of a drop in domestic public support for their continued presence, have been scaling back their forces.
"Our allies are not in a position to provide them (extra troops), so we are now looking at perhaps carrying a bit of that additional load," Morrell said.
In Brussels, NATO Secretary-General Jaap de Hoop Scheffer welcomed the U.S. plans but pointed to recent smaller additions from countries such as France, Slovakia, Hungary and Poland -- which on Wednesday announced it would add 400 troops and helicopters -- to its existing 1,200-strong contingent.
"You cannot say the allies are not active enough, because they are active. ... But I still think we can do better," he told reporters at an event in Brussels, noting persistent shortfalls in NATO's forces.
He also stressed the ultimate answer was not military but a long-term commitment to reconstruction and development.
"The solution for Afghanistan is not pouring in tens of thousands of forces," he said.
About half of the 30,000-member U.S. troop contingent serves in the 40,000-strong NATO-led International Security and Assistance Force, while the rest conduct missions ranging from counter-terrorism to reconstruction to training Afghan troops.
While NATO says it squelched last year's Taliban spring offensive, overall violence is up 27 percent from a year ago and has risen by 60 percent in the southern province of Helmand, the U.S. military said last month.
De Hoop Scheffer argued that other good news from the country, such as a doubling in the average Afghan personal income from 2001, was being overshadowed by the violence.