More American troops will stay behind in Afghanistan next year than originally expected.

According to inside sources, the U.S. is preparing to increase the number of troops that will remain in Afghanistan in 2015 in order to make up for the gap left in the NATO mission by other contributing nations, reports Reuters exclusively.

A report published on Tuesday stated that Washington may provide up to 1,000 extra soldiers under the U.S. commitment described as a "bridging solution" until other nations fulfill their pledges or the troops are no longer needed. Informed sources, however, did not give an exact number of additional troops that will stay in Afghanistan.

The additional U.S. troops will be assigned to a NATO force of 12,000 in Afghanistan and work to train, advise and assist Afghan forces, said the unidentified sources.

Although the coalition force in Afghanistan did not comment on the figures, it said that it welcomed all commitments of troops to the new NATO-led mission.

"We are confident that we will have the necessary resources to launch the Resolute Support mission on Jan. 1, 2015. The process to generate the forces required for the mission is ongoing," the International Security Assistance Force said.

The majority of U.S. combat troops are to leave the country at the end of December as the 13-year war in Afghanistan finally comes to an end.

Back in May, President Barack Obama announced that our military presence would be drastically cut to 9,800 troops by the end of 2014. The number of troops are also scheduled to be cut by half in 2015 and then dwindle to a normal embassy presence by the end of 2016.

"There will be 9,800 troops, plus at least a few hundred above and beyond that," the source said.