The president is also expected to announce tonight the deployment of a second aircraft carrier -- perhaps the USS Stennis -- to the Persian Gulf, as part of a regularly scheduled deployment. Centcom Commander Gen. John Abizaid has requested a second carrier because of Iran and other threats in the region.
The ship will leave next weekend on its regularly scheduled departure date, but will proceed to the Gulf instead of its original deployment to the Pacific.
Commanders believe the new approach will make U.S. forces better positioned to combat sectarian violence, but they acknowledge this approach is riskier and will likely mean more U.S. casualties in the short-run.
In al-Anbar Province, an additional 4,000 Marines will focus on fighting al Qaeda to try to take advantage of what U.S. commanders say is a new willingness of some Sunni tribal leaders to cooperate in the fight against the international terrorist organization.
The increase in U.S. forces will be completed within 90 to 120 days.
ABC News has also learned that National Guard troops who have seen combat in Iraq and Afghanistan will likely be getting some unwelcome news: They may have to go back to Iraq later this year. National Guard combat teams would be sent to Iraq as the next wave of the surge, unless the first wave succeeds in reducing the violence.
Commanders here caution it will take several months to fully implement the plan and maybe even longer to see results. As one senior military official here said Wednesday, "We don't know if this will work, but we do know the old way was failing."
ABC News' Jake Tapper and Martha Raddatz contributed to this report.