President Bush on Saturday remembered the Sept. 11 terrorist attacks and the strength of U.S. citizens and troops who rallied to defend the nation, saying the United States and its allies will continue to fight extremists and terrorists "head on."

Bush marked the seventh anniversary of the attacks on Thursday with a moment of silence at the White House and a dedication ceremony for a new Sept. 11 memorial at the Pentagon. On that day in 2001, terrorists crashed a hijacked airliner into the World Trade Center in New York. A second plane struck the trade center shortly thereafter. Another plane was flown into the Pentagon and still another crashed in a field at Shanksville, Pa. Nearly 3,000 people died, including 184 at the Pentagon.

"In the years to come, parents will visit this site to remember children who boarded Flight 77 for a field trip and never emerged from the wreckage," Bush said in his weekly radio address, referring to the American Airlines jet that crashed into the Pentagon. "Husbands and wives will visit the memorial to remember spouses who left for work one morning and never returned home. And people from across our nation will visit to remember the heroism of rescue workers who rushed into the burning Pentagon to save the lives of their fellow citizens."

Bush announced this week that he will pull about 4,000 troops out of Iraq before the end of the year and another 4,000 in January. But the troop withdrawals were not as large or as swift as expected and the 138,000 total that will remain is higher than the troop strength in January 2007 when Bush ordered the military buildup. At the same time, Bush announced he was sending one Marine battalion to Afghanistan in November to replace two that are scheduled to leave and an Army brigade there by January.

Bush said that in Afghanistan, where the Sept. 11 attacks were planned, U.S. troops toppled the hardline Taliban regime, destroyed Al Qaeda camps and helped create a democracy.

"In the years since, members of the Taliban and Al Qaeda have sought to regain power through acts of terror," Bush said. "The United States and our allies are meeting this challenge head on. We will not allow Afghanistan to once again become a safe haven for terror."