WASHINGTON — Under pressure from Congress, the Bush administration reversed gears yesterday and released a report showing an upsurge in terrorist attacks worldwide in 2004 after first withholding the statistics from the public.

The number of "significant attacks" grew to about 651 last year, from 208 in 2003, according to statistics released by the National Counterterrorism Center. The 2004 total includes 201 attacks in Iraq.

The totals raised questions about the administration's claims that it is winning the war on terrorism.

But senior officials said the threefold increase was a result of changes in methodology and urged reporters not to compare this year's terrorism numbers with previous ones.

"The numbers can't be compared in any meaningful way," said John Brennan, acting head of the center, which compiled the statistics. He said his agency had revamped the process of counting terrorist attacks after last year's embarrassment in which the State Department withdrew its first report and admitted it had significantly understated what turned out to be a record number of attacks.

This year, Brennan said, 10 full-time intelligence analysts — up from three part-timers — searched for terrorist incidents to include, resulting in a much higher total than met the government's criteria for classification as a "significant" attack.

Although the officials called the data seriously flawed, they said they issued the report to avoid criticism that the State Department was trying to avoid admitting setbacks in the fight against terrorism by not publishing the data.

"If we didn't put out these numbers today, you'd say we're withholding data. That's why we're putting them out," said Philip Zelikow, counselor to Secretary of State Condoleezza Rice.

The Knight Ridder News Service reported the administration's plans to withhold the terrorist-attack statistics in mid-April.

The annual report on global terrorism, compiled by the State Department, warned that while al-Qaida leaders have been hurt by military operations, local groups inspired by the terrorist network launched deadly attacks in Spain, Indonesia and elsewhere.

"There is a declining role for a significantly degraded al-Qaida and a rising role for groups inspired by al-Qaida," Zelikow said.

The totals include only attacks on noncombatants by terrorists, so the 201 attacks in Iraq don't include roadside bombs that killed U.S. and coalition soldiers. There were 22 terrorist attacks in Iraq in 2003, after the U.S.-led invasion.

Attacks by remnants of the Taliban also increased from 14 to 27 in Afghanistan, and the report recorded about 300 attacks related to the Pakistan-backed Muslim insurgency against India in Kashmir. Pakistan is a U.S. ally in the war on terrorism.

Rep. Henry Waxman, D-Calif., who pressed for release of the data, said in a letter to Rice that the increase "may undermine administration claims of success in the war on terror."

The sharp increase in terrorist attacks "can't be explained away as a mere methodological artifact," Waxman said.

The State Department report touted better international cooperation for foiling some terrorist plans and said two nations that have supported terrorism, Libya and Sudan, had improved their cooperation.

The terrorist attacks last year claimed about 9,000 victims, including 1,907 people killed. In 2003, 625 people were killed.

The counterterrorism center is working on a new list, to be released in June, that will use new, more realistic, definitions of terrorism. It likely will include more incidents, Brennan said.

As an example, Brennan said, the report lists only one of two Russian airliners that suicide bombers blew out of the sky last year. The one that counted had an Israeli aboard. The other had all Russians, making it a domestic incident.

"It makes no sense to have the definition of terrorism depend on checking the nationality of all the victims," Brennan said.

This report includes material from The Washington Post and The Associated Press.