Four years ago at a luxury Houston hotel, oil company adviser Zalmay Khalilzad was chatting pleasantly over dinner with leaders of Afghanistan's Taliban regime about their shared enthusiasm for a proposed multibillion-dollar pipeline deal.

Today, Khalilzad works steps from the White House, helping President Bush and his closest advisers in attempts to annihilate those same Afghan officials.

From his perch as a member of the National Security Council and special assistant to the president, the Afghanistan native is one of the most influential voices on Afghan policy.

He is the only White House official to have lived in Afghanistan, and he has a visceral feel for the region's tensions and history. His long-term influence on matters pertaining to Central Asia is made apparent by a photo in his office in the Eisenhower Executive Office Building. Snapped next door at the White House, it shows President Ronald Reagan and Khalilzad huddled in discussion with an Afghan leader, who at the time was battling to oust the Soviets.

"Zalmay is the ideal man for Afghanistan, because he is an Afghan himself and he's grown up there and knows the country," said Richard Dekmejian, a specialist in Islamic fundamentalism at the University of Southern California and an acquaintance for more than a decade. "He brings firsthand knowledge of the country together with the perspective of a policy expert. He's at the right place."

Since the 1980s -- as a Reagan administration policy planner, a consultant, a Pentagon strategist and a Rand Corp. scholar -- Khalilzad, a U.S. citizen, has been in contact with myriad squabbling Afghan warlords and political leaders.

Over the decades, he has evolved from a Cold War activist, celebrating the retreat of Soviet forces from his homeland, to a more moderate voice, calling for friendly persuasion with the Taliban. Now, he is a hawk urging the Taliban's destruction.

His evolving views are evident in a long string of journal articles, position papers and newspaper columns.

"The Taliban does not practice the anti-U.S. style of fundamentalism practiced by Iran," Khalilzad wrote four years ago in The Washington Post. "We should . . . be willing to offer recognition and humanitarian assistance and to promote international economic reconstruction. . . . It is time for the United States to reengage" the Taliban.

More recently, though, he began stressing that action against the Taliban "now is essential."

"The danger is growing," he wrote late last year with Daniel Byman of the Rand Corp. in Washington Quarterly, a policy magazine. "Soon the movement will be too strong to turn away from rogue behavior. It will gain more influence with insurgents, terrorists and narcotics traffickers and spread its abusive ideology throughout the region. . . . Alternatives to confrontation have little promise."

Khalilzad was born 50 years ago in the northern Afghan city of Mazar-e Sharif, 70 miles south of the Soviet border. While still young, his family moved to the regional capital of Kabul, where his Pashtun father worked in the government, which was then a monarchy.

"They certainly would have been people among the intellectual elite of the time," said Thomas E. Gouttierre, director of the Center for Afghanistan Studies at the University of Nebraska at Omaha. "They became Kabuli, the Parisians of Afghanistan: urbane, urbanized people."

Khalilzad's first glimpse of the United States came as a teenager, when he visited this country in a student exchange program run by the American Friends Service Committee, a Quaker charitable organization, Gouttierre recalled. Khalilzad went home with a passion for American culture, including basketball.

"He saw and played basketball while in the U.S.," said Gouttierre, who coached Khalilzad on a student team. "As it turned out, he was not a great player. I knew then he would be a better intellectual than a basketball player."

After completing high school in Kabul, Khalilzad earned an undergraduate degree from the American University in Beirut, followed by a doctorate in political science from the University of Chicago in 1979 -- the same year the Soviets invaded his homeland.

For the next decade, Khalilzad was an assistant professor of political science at Columbia University, also serving as executive director of the Friends of Afghanistan, a support group for the Afghan mujaheddin then battling the Soviets.

From 1985 to 1989, Khalilzad worked at the State Department as a special adviser to the undersecretary of state, consulting on the Iran-Iraq War and on the Soviet war in Afghanistan. He belonged to a small group of policymakers who successfully pressed the Reagan administration to provide arms -- including shoulder-fired Stinger missiles -- to anti-Soviet resistance fighters in Afghanistan.

He then served as undersecretary of defense in the first Bush administration while it waged war against Iraq. Later, he worked as a senior political scientist at Rand, a consulting company that performs policy studies for the U.S. military. He directed strategy for Rand's Project Air Force and founded the corporation's Center for Middle Eastern Studies.

He also joined the board of the Washington-based Afghanistan Foundation, a nonprofit corporation dedicated to raising interest in the country. He became the primary author of a foundation position paper that urged U.S. officials to prod the Taliban and its opposition toward joining forces in a new, broad-based government.

During the mid 1990s, while at the for-profit Cambridge Energy Research Associates, Khalilzad conducted risk analyses for Unocal Corp., a U.S. oil company that hoped to construct gas and oil pipelines across Afghanistan. At the time, Unocal held signed business agreements with the Taliban.

In December 1997, Unocal brought top Taliban leaders to the United States to view its operations in Houston. Khalilzad joined Unocal officials at a reception for the visiting Taliban delegation. Over dinner, Khalilzad challenged the leaders on their treatment of women, whom the Taliban jailed for failing to cover their faces with veils. His debate with Amir Khan Muttaqi, Taliban minister of culture and information, escalated into a spirited dissection of the precise language of the Koran.

Khalilzad's wife, Cheryl Bernard, is an Austrian writer and feminist whose novels champion women's rights.

Over the years, Khalilzad has written and edited books with such titles as "Strategic Appraisal: The Changing Role of Information in Warfare," "United States and Asia: Toward a New U.S. Strategy and Force Structure" and "Aerospace Power in the 21st Century." He also co-wrote, with his wife, "The Government of God: Iran's Islamic Republic."

After Bush's victory last November, Khalilzad headed the Bush-Cheney transition team for the Defense Department. He also counseled Defense Secretary Donald H. Rumsfeld. In his current role, he answers directly to national security adviser Condoleezza Rice.

"He is scholarly, cool. Always a smile. Outgoing," Dekmejian said. "He's not a preacher type, one who goes out there and moves the masses. But he is very good at addressing small groups of people. He is not an arrogant government person. He has an open mind."

Gouttierre said the White House is lucky to have an expert in diplomacy and military affairs who also has a gut-level feel for the politics of Afghanistan.

"He's the right kind of a guy at the right place right now," he said.

Zalmay Khalilzad, left, with Defense Secretary Donald H. Rumsfeld, was born in Afghanistan and is a U.S. citizen.