The White House is preparing to send Congress an amendment to its $100 billion war supplemental request as early as today, though the Office of Management and Budget would not disclose any information on the proposed changes at press time.

In turn, Senate Appropriations Chairman Robert Byrd (D-W.Va.) has put his emergency supplemental draft on hold until he receives the administration’s proposed modifications, which effectively hits the pause button on adding emergency funding for the home front. The House’s supplemental bill contains billions in add-ons unrelated to overseas military operations, including $4.3 billion in agricultural disaster assistance and $1 billion for pandemic flu preparedness initiatives.

Byrd’s supplemental legislation will likely track the House version by replenishing the $3.1 billion in Base Realignment and Closure funding that was shifted to boost domestic programs in the fiscal 2007 joint funding resolution. Byrd also is working with Sens. Mary Landrieu (D-La.) and Thad Cochran (R-Miss.) on drafting an aid package for the hurricane-damaged Gulf Coast.

Other than additional BRAC funding and Gulf Coast assistance, Byrd will wait to assess the president’s supplemental amendment before moving on any other domestic spending decisions, a source said.

Though details of the White House plan were not yet available, some signals emerged earlier this week when Deputy Secretary of Defense Gordon England testified at a House Budget Committee hearing Tuesday.

England told the panel that the Pentagon would be sending at least 4,000 logistics and support personnel to Iraq to sustain the additional 21,500 combat troops currently en route to Baghdad and Anbar province. England said that the extra support troops would cost “somewhat over $1 billion” and that the Defense Department is eyeing the proposed funding for two Joint Strike Fighters as potential offsets.

The administration requested the JSFs as replacements for an F-15 and F-16 lost during battle, but the JSFs are not expected to be combat-ready until 2010.