The request, which will fund U.S. combat operations in Afghanistan until the White House's 2014 drawdown deadline, will be delivered to lawmakers "in the next few weeks," Deputy Defense Secretary Ash Carter said Tuesday.
Past OCO funding requests have been sent alongside the Pentagon's baseline budget plan.
But with the Pentagon coping with massive, across-the-board cuts under the administration's sequestration plan, Department of Defense (DOD) officials needed more time to build the OCO request around those cuts, Carter said during a speech in Washington.
Recent reports claim it will cost DOD roughly $6 billion just to move the mountain of weapons, vehicles and equipment out of Afghanistan and back to the United States in time for the 2014 drawdown deadline.
But outstanding questions on what Washington's role will be in postwar Afghanistan, both militarily and politically, have also contributed to the delay, he added.
"Not all of those decisions have been made," by the White House and its allies regarding the American postwar presence in Afghanistan after 2014, Carter noted.
Washington and Kabul have yet to finalize a postwar plan, outlining how many U.S. troops will remain in Afghanistan after the deadline and what their mission will be.
"The inevitable amount of estimation" needed to forecast war spending over the next two years, without a viable postwar policy plan and with the effects of sequestration, has made war planning in the Pentagon a challenge, he said.
The department's pending request to Congress to shift nearly $7.5 billion in FY '13 funds from base costs to war spending has helped ease that challenge, according to Carter.
That said, Carter reiterated the dangerous impact sequestration was having on U.S. military planners, trying to develop a national security strategy beyond Afghanistan.
Even though Afghan war funding is all but locked up, sequestration is continuing to impact the department's "capability to respond to the unforeseen."
With looming threats such as Syria, Iran and North Korea, the fiscal pressures coming from sequestration "is not only stupid, it is not safe," Carter said.
Sign up to receive overnight updates via email here.