The Obama administration is finalizing a report on the U.S. nuclear-force structure and may send it to Congress this month.

The update to the so-called 1251 report outlines the United States’ 10-year plans for maintaining its nuclear-weapons complex. The initial report was required by section 1251 of the fiscal year 2010 National Defense Authorization Act, and the FY ‘12 version of the law requires the White House send Congress an update with its budget request every year.

Defense Secretary Leon Panetta and Energy Secretary Steven Chu sent Senate Armed Services Committee Chairman Carl Levin (D-Mich.) a March 2 letter saying they will submit separate 10-year plans for the nuclear complex to Congress. The Pentagon’s report will arrive in the “coming weeks,” the letter said.

“The Congress is now left without the long-term data to determine whether we are making the investments to ensure our (Department of Defense) DoD delivery platforms and DoD infrastructure are on a sustained path for modernization,” Senate Armed Services Strategic Forces subcommittee Chairman Ben Nelson (D-Neb.) lamented at a March 28 hearing.

Madelyn Creedon, assistant secretary of defense for global strategic affairs, told the subcommittee at that hearing Pentagon officials “obviously recognize that the report is late.”

“With the reductions that needed to be made in the defense budget (because of the Budget Control Act of 2011), there were also obvious adjustments in the strategic enterprise,” Creedon said. “So we needed some time to look at the long-term impact of the reductions that were made in the (FY) ‘13 budget, for instance, a two-year delay of the SSBN(X) (ballistic-missile submarine).”

She said Pentagon officials were “in the process of completing that report,” saying “hopefully if it doesn’t take too terribly long to get through all the various review procedures in the department, we would hope that it would be provided in weeks.”

The timeframe would be in “weeks, not months…hopefully in April,” she added.

When the Senate approved the U.S.-Russia New Strategic Arms Reduction Treaty (New START), it attached a condition saying the United State will fund maintenance of the weapons-production-complex in line with levels in the initial 1251 report.

The subsequent reports are intended to provide updates on the nuclear-complex plans, and how they differ from the initial 1251 report. Republicans including House Armed Services Strategic Forces subcommittee Chairman Michael Turner (R-Ohio) are trying to force the administration to heed nuclear funding levels from the baseline 1251 report.

Sen. John Cornyn (R-Texas) expressed concern at the SASC Strategic Forces hearing about the administration’s FY ‘13 budget request falling $372 million short of that initial 1251 plan, and five-year funding being $4 billion less.

Creedon said she is comfortable with the FY ‘13 funding request being “a little bit less than what was projected to be in ‘13 in the 1251 report,” saying it’s “only a little bit less and it’s more than the appropriated amount in ‘12.”

“We’ve made some adjustments in the some of the scheduled programs, but ‘13 is OK,” she said. Still, she told Cornyn “where we are all concerned and where we have work to do is in the outyears.”

Observers point out that Congress did not fully fund the administration’s request for so-called 1251 report activities in FY ‘12. It “not likely to do so” in FY ‘13 either, the Washington-based Arms Control Association predicts in a March 19 report.

Creedon, meanwhile, told the SASC Strategic Forces panel the Pentagon has started working on New START by getting rid of so-called phantom assets–those already retired–targeted for elimination under the treaty. Those phantoms include 50 previously retired Peacekeeper silos, 50 previously retired Minutemen III silos, and B-52 H-bombers.

“The initial focus is addressing these phantoms, systems that are no longer in active service,” she said. “After that, then we’ll move on to what the active reductions will be. The assumption at the moment is that the active reduction decisions will be made at the end of the year, shortly after the year but in the context of the FY ‘14 budget.”