At both events, Karzai referred to the days before U.S.-led forces invaded Afghanistan, deposing the ruling Taliban and scattering the leadership of Al-Qaeda, which operated there, plotting the attacks in the United States on 11 September 2001.
In his remarks to Congress, Karzai said: "Afghanistan has emerged from a very dark era, one of oppression and terror. We have adopted an enlightened constitution, establishing a democratic, Islamic government. It guarantees equal rights and equal protection for every citizen of our country."
Karzai then recounted the reforms in his country since the Taliban was defeated, including education for girls as well as boys, improved health care, a free press, improved infrastructure such as roads, and training for a new national army. He also cited national elections, which are scheduled for September.
None of this would have been possible without the help of the United States and other countries, Karzai told Congress in an address that was repeatedly interrupted by applause.
But the chairman of the Afghan Transitional Administration also acknowledged that problems remain, particularly the widespread cultivation of opium poppy. He said his government is working hard to stop the drug trade for the sake of his own people and those in regions where the drugs are used.
"We have initiated the fight against narcotics to save our children, to save your children, and to save children across the world from the evil of addiction to drugs," he said.
To do so, and to continue the other improvements in his country, Karzai urged the lawmakers and business leaders to continue the help that Afghanistan already has received. Specifically, he called for a free-trade agreement between his country and the United States.
With both governmental and corporate help, Karzai said, Afghanistan will become a modern success story in good governance. "To succeed, we ask for your continued investment. Afghanistan is open for business and American companies are most welcome. Together, we will make Afghanistan a great success and an enduring example of a prosperous, democratic society," he said.
Later, at the White House, he elaborated on the theme of Afghanistan's progress, calling its constitution "the most enlightened in that part of the world." He said it is proof that democracy and Islam can co-exist.
But Karzai said his job as president is to make his country advance even further by engaging all Afghans and ensuring that the September elections proceed as smoothly as possible.
"It's my job to take that nation, the Afghan people to a better future, to stability and peace, to a higher degree of democracy, to the elections. It's my job to do that peacefully. It's my job to keep stability and peace in Afghanistan. And I will talk to anyone who has come to talk to me about stability and peace and about movement towards democracy," Karzai said.
Karzai also expressed resentment at criticism of him for having dealings with Afghanistan's heavily armed regional leaders, most of whom are referred to as "warlords." He said that as president, it is his responsibility to deal peacefully with all sectors of Afghan society in an effort to promote democracy. No deals have been made with these regional leaders, Karzai said, and no coalitions have been formed between them and his government.