KABUL, Afghanistan — Eight years ago, Mahmoud Karzai was running a handful of modest restaurants in San Francisco, Boston and Baltimore. Today, Mr. Karzai, an immigrant waiter-turned-restaurant owner, is one of Afghanistan’s most prosperous businessmen.

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Lynsey Addario for The New York Times

DIVERSE INTERESTS Mahmoud Karzai has invested in an apartment complex in Kabul, above, a cement factory, mines and a Toyota distributorship.

The older brother of Hamid Karzai, the Afghan president, Mahmoud Karzai has major interests in the country’s only cement factory, its dominant bank, its most ambitious real estate development, its only Toyota distributorship and four coal mines.

He and a business partner run Afghanistan’s national Chamber of Commerce — which has far more clout than its American counterpart — allowing him to broker deals and lure foreign investors. For executives with problems with the Afghan government, he is the man to see. One prominent Afghan critic describes him as a “minister maker” with sway in hiring and firing top officials.

An unabashed advocate for money-making in the country his brother runs, Mr. Karzai attributes his success to having big ambitions and taking on ventures that others saw as too risky. “I’m investing in projects that require real work,” he said in an interview. “I’m in love with the idea that Afghanistan can become a Singapore, a Hong Kong.”

Mr. Karzai, though, clearly has exploited his connections, both in Washington and Kabul, to build his business empire. He has collected millions in American government loans for real estate developments in Kandahar and Kabul, capitalized on a friendship with Jack Kemp, the former Republican congressman, for introductions to American officials and international business executives, and benefited from what his rivals charge were sweetheart deals with the Afghan government.

Mr. Karzai’s swift rise has stirred resentment and suspicion among many Afghans, who have grown disaffected with the Karzai government and its seeming tolerance for insider dealing, favor trading, bribe taking and other unsavory activities. Rampant corruption fuels the Taliban insurgency, experts warn, and threatens American support for President Karzai, who is seeking re-election this year.

While Mahmoud Karzai has not been accused of any criminal wrongdoing, he has become a political liability, with critics complaining that his ascent was unfairly eased.