CBS News national security correspondent David Martin reports that President Bush will make what could well be his last major decision on the Iraq War - an issue that has dominated and defined his presidency.
Acting on recommendations made by Defense Secretary Gates, the president will announce the withdrawal of 8,000 troops from Iraq by next February. A battalion of 1,500 Marines out of western Iraq in November and an Army combat brigade of 3,500 soldiers will be withdrawn in February, along with 3,400 support troops.
That will bring overall troop strength in the country down to 136,000 - about what it was in 2006 before the "troop surge" was announced.
The president will say the withdrawals are possible because of the dramatic reductions in violence, now down to the lowest level since the spring of 2004.
The measured reduction - slower in scope and pace than many Democrats in Congress would like - gives the military some flexibility to shift forces into Afghanistan.
"Here is the bottom line: While the enemy in Iraq is still dangerous, we have seized the offensive, and Iraqi forces are becoming increasingly capable of leading and winning the fight," Mr. Bush said in remarks prepared for delivery to the National Defense University in Washington.
But even these modest withdrawals - less than six percent of U.S. troops - are more than the commander in Iraq, General David Pretraeus originally wanted. He recommended no further reductions until June of next year.
But he was overruled by because of the pressing need to free up more troops for Afghanistan.
The president will announce he is sending 5,000 more combat troops to Afghanistan: a Marine battalion in November and army combat brigade next January, but that is only a fraction of what the commander there says he needs.
President Bush will say it may be possible to withdrawal more troops in the first half of 2009 but that will be a decision for the next president.
In his remarks Mr. Bush argued that Iraq is in a better place now by almost any measure. He said violence is at its lowest point since the spring of 2004, "normal life is returning to communities across the country," and political reconciliation is moving forward.
The president cautioned that progress is still fragile and could be reversed. But he said his top commander and diplomat in Iraq assure him that the gains made there now have some durability.
But all this emphasis on progress and improvement belied the fact that his announcement is likely to be a disappointment to many who wanted - and even expected - bigger drawdowns sooner.
Nowhere did Mr. Bush acknowledge this, instead highlighting his announcement as one of "additional force reductions."
The Iraq war has drained the country's spirit during Mr. Bush's second term, and the future course of the conflict is a major point of division between the men who want to replace Mr. Bush, Republican Sen. John McCain and Democratic Sen. Barack Obama.
More than half of Mr. Bush's address is devoted to Afghanistan.
He outlined what he called a "quiet surge" of additional American forces there, bringing the U.S. presence to nearly 31,000, compared with about 146,000 in Iraq.
"For all the good work we have done in that country, it is clear we must do even more," the president said.
He announced that a Marine battalion that had been scheduled to go to Iraq in November would go to Afghanistan instead, and that that would be followed by one Army combat brigade.
Commanders repeatedly have asked for more troops in Afghanistan, where there has been a resurgence of the Taliban and a growth in violence. The president acknowledged that the challenges in Afghanistan remain huge.
"Unlike Iraq, it has few natural resources and has an underdeveloped infrastructure. Its democratic institutions are fragile," Mr. Bush said. "And its enemies are some of the most hardened terrorists and extremists in the world. With their brutal attacks, the Taliban and the terrorists have made some progress in shaking the confidence of the Afghan people."
In other developments: