Washington ? President George W. Bush is paying tribute to the global coalition against terrorism and previewing the war’s next phase as more than 1,000 people gather at the White House to mark the six-month anniversary of the Sept. 11 terrorist attacks.

Bush invited more than 100 ambassadors to the South Lawn on Monday to commemorate the day six months ago that New York’s World Trade Center and the Pentagon were attacked. Among those also attending were members of Congress, relatives of some 300 victims and top administration officials.

Preparing for the event Sunday, crews assembled an enormous stage facing south away from the White House.

Bush planned to offer a “broad outline of what’s been accomplished and where we are headed, the challenges we face as the war on terrorism continues,” White House spokesman Gordon Johndroe said.

A primary focus of the president’s speech was an acknowledgment of the importance of the global coalition against terror, Johndroe said. A tribute to victims of the New York and Pentagon attacks and the deliberate crash of an airliner in Pennsylvania also was planned.

Bush was to declare that the United States and its allies cannot afford to do nothing as “rogue” nations work to develop weapons of mass destruction, but he was not expected to single out which nations he might target for the next phase.

As American forces made new advances against the last known major pocket of al-Qaida resistance in Afghanistan, the president planned to offer a more detailed outline of the administration’s plans to stamp out the terrorist network.

“I realize we’re in for a long struggle,” Bush said last week in Florida. “I’m giving a speech on Monday that will outline where we are in this war on terror, and I’m going to remind the American people that we’ve still got a task at hand in Afghanistan, which is to deny sanctuary to al-Qaida killers.”

Elsewhere Monday, Environmental Protection Agency Administrator Christie Whitman and emergency management chief Joe Allbaugh were marking the attacks in New York City.

At the Pentagon, Defense Secretary Donald Rumsfeld was meeting with military leaders from the nations in the anti-terrorism coalition.

Rumsfeld was to lead a tour of Pentagon reconstruction, and have a working lunch with the leaders.

In London, Vice President Dick Cheney, starting a 10-day foreign tour, was joining British Prime Minister Tony Blair to commemorate the attack on the United States and remember the citizens of the many nations who were lost Sept. 11.