Veteran CIA officer Tyler Drumheller on “60 Minutes” in 2007. (Courtesy of CBS)

Tyler S. Drumheller, a high-level CIA officer who publicly battled agency leaders over one of the most outlandish claims in the U.S. case for war with Iraq, died Aug. 2 at a hospital in Fairfax County. He was 63.

The cause was complications from pancreatic cancer, said his wife, Linda Drumheller.

Mr. Drumheller held posts in Africa and Europe over a 26-year career during which the CIA’s focus shifted from the Cold War to terrorist threats. He rose to prominent positions at CIA headquarters, serving as chief of the European division at a time when the agency was abducting al-Qaeda suspects on the continent and U.S. allies there faced a wave of terrorist plots.

But he was best known publicly for his role in exposing the extent to which a key part of the administration’s case for war with Iraq had been built on the claims of an Iraqi defector and serial fabricator with the fitting code name “Curveball.”

In contrast to Hollywood’s depiction of spies as impossibly elegant and acrobatic, Mr. Drumheller was a bulky, rumpled figure who often seemed oblivious to the tufts of dog hair on his clothes.

“I always thought of him as an overfed George Smiley,” said Bill Murray, a former CIA colleague, referring to the character in John le Carré spy novels known for his espionage acumen but unassuming appearance.

Mr. Drumheller spent the bulk of his career as an undercover officer seeking to avoid public attention. But after retiring in 2005, he emerged as a vocal critic of the George W. Bush administration’s use of deeply flawed intelligence to build support for its decision to invade Iraq in 2003.

Curveball, who had defected to Germany in the late 1990s, was the primary source behind the administration’s assertions that Saddam Hussein’s regime in Iraq had developed biological weapons laboratories — lethal germ factories supposedly built on wheels or rails to evade detection.

The claim was included in Bush’s 2003 State of the Union speech as well as then-Secretary of State Colin Powell’s presentation to the United Nations designed to marshal international support for intervention in Iraq.

Mr. Drumheller later came forward to say that he had learned early on that German authorities had grave doubts about Curveball’s credibility. In his book “On the Brink” (2006), written with Elaine Monaghan, he recounted the Curveball debacle in detail, noting that his German counterpart had cautioned that Curveball “could be a fabricator. He’s a very erratic character.”

Mr. Drumheller said he relayed that warning to top CIA officials, and even attempted to strike the language on mobile labs from an early draft of Powell’s speech, only to be stunned to learn that the text was subsequently restored.

In “On the Brink,” Mr. Drum-heller described feeling his “heart sinking” as he watched Powell’s speech.

“We had failed,” he wrote. “It was bad enough that we had not prevented the Sept. 11 attacks and we were being blamed for that. Now the nation was about to embark on a war based on intelligence I knew was false, and we would surely be blamed for that, too.”

A scathing 2005 report on the intelligence failures in Iraq did not mention Mr. Drumheller by name but concluded that officials in the agency’s European division had “expressed serious concerns about Curveball’s reliability to senior officials at the CIA,” and that the warnings were inexplicably dismissed.

The allegation touched off a bitter feud. When then-CIA Director George J. Tenet denied that he had ever been warned about Curveball, Mr. Drumheller fought back in public, saying that “everyone in the chain of command knew exactly what was happening.”

Mr. Drumheller was widely quoted in news accounts and appeared on the CBS program “60 Minutes.”

No mobile germ warfare labs were found, and the defector, Rafid Ahmed Alwan al-Janabi, has since admitted that the story was a fiction he fed to German intelligence while seeking asylum.

The blow-up over Curveball coincided with Mr. Drumheller’s retirement from the CIA. “I think he was really proud of standing up against the war,” Linda Drumheller said in an interview. “That was his personal greatest achievement.”

The son of an Air Force chaplain, Tyler Scott Drumheller was born in Biloxi, Miss., on April 12, 1952. He spent part of his childhood in Germany before attending the University of Virginia. He graduated in 1974 with a history degree and did postgraduate work in Chinese at Georgetown University before being hired by the CIA in 1979.

He met Linda Blocher while she was working at the spy agency as a secretary in the Africa division, and proposed to her in a stairwell at CIA headquarters after learning that he would soon be sent to Zambia. It was the first in a series of stops for the couple that would also include South Africa, Portugal, Germany and Austria. Two and sometimes three pet dogs accompanied every move.

Besides his wife, of Vienna, Va., survivors include a daughter, Livia Phillips of Great Falls, Va.; a sister, Alecia Ball of Chester, Va.; and a grandson.

Mr. Drumheller’s affable manner made it easy for him to form lasting connections with people throughout his career, Linda Drumheller said. He also had a prodigious memory, she said, that enabled him to keep track of cryptonyms, children’s birthdays and Detroit Tigers statistics.

Mr. Drumheller “understood human nature,” Murray said. “Beneath that pleasant and fun kind of personality, he understood exactly what people were and what he was dealing with. Good or bad.”

Mr. Drumheller had retained a young CIA recruit’s enthusiasm for much of his career. But he seemed to grow tired of the internal conflicts after the Sept. 11 attacks. In his memoir, he wrote that in retirement he asked to have his Distinguished Career Intelligence medal delivered by mail rather than returning to headquarters for a ceremony.

When the envelope arrived, he wrote, “I opened it up and fell into a bit of a reverie, reflecting on my career and the years past, the successes and the friends gained, the colleagues lost and the mistakes made.”