After seven years, French Ambassador Francois Bujon de l'Estang returns home Sunday on a high note in bilateral relations and leaving "a big chunk" of himself behind. He has grown to cherish Washington in three different incarnations -- as a junior diplomat, as a businessman and as an ambassador -- and not only because the city was designed by a Frenchman.

Despite the chronically prickly French-U.S. relationship, Bujon departs with a renewed understanding of the "odd-couple" alliance, even when both sides start out disagreeing. Exhibit A is the resounding diplomatic achievement of the unanimous U.N. Security Council resolution on Iraq. After seven weeks of feverish bargaining among the United States, France and other powers, inspectors are back in Baghdad for renewed scrutiny of suspected sites of weapons of mass destruction.

In his waning days here, Bujon found himself looking back with a deepened regard for the American people's resilience and sense of optimism, and the dynamics of a free-market economy, he said in a lengthy interview at his sprawling chancery on Reservoir Road.

The ambassador said he observed firsthand the "extraordinary vitality" of Americans after years of striking prosperity and economic growth. Since the tragic events of Sept. 11 last year, "I have seen a country that feels at war and is at war. . . . The age of innocence is gone for good. I have admired how Americans have rallied around their flag, their basic values and [their] president."

"We are true friends of the United States, because we speak up when we differ in our judgment. We consider this the duty of a true friend," he insisted, "like an odd couple who stay together for good or for bad." Despite the emotional flare-ups, "we are America's oldest ally. We have been there from Day One," he emphasized. "And when the going gets tough and when push comes to shove," continued the ambassador, "we have views on world affairs and we express them, but in the end, the French are also bad-weather friends."

"The knack for irritating one another" notwithstanding, the value of the U.S.-French friendship, he said, became apparent to him during the seven weeks of intense debate at the United Nations, which concluded with French President Jacques Chirac calling Syrian President Bashar Assad at the eleventh hour with convincing arguments to go along with a vote that the rest of the world, including Iraq, would end up accepting.

Throughout the period of diplomatic wrangling, the embassy was flooded with letters, telephone calls and e-mail from all over the country -- 10,000 in all, according to French press attache Nathalie Loiseau, who kept track.

"We got very interesting mail. There were some insults, but the vast majority were letters of encouragement that did not express opposition to American leadership or its stance on Iraq, but which made the point: 'Yes, you are right to make an effort at internationalizing this issue, so the United States should not have to go it alone,' " Bujon said. "The letters proved that Americans were concerned about Iraq's weapons of mass destruction, but had great misgivings about the U.S. going into military action that would not have the support of its allies," he added.

Cultural and political misconceptions of what both countries represent proved to be a thorn in Bujon's side during his time here. "Frequently, they are completely false, such as notions that French foreign policy is too high-profile or too ambitious compared to its real power," he pointed out. He called "theme-park" visions of France "antiquated." There is a kind of suspicion about France, "but the French do not wake up every morning asking themselves how to aggravate the United States; this is not what drives us," he explained.

Still, Americans are very open-minded, he said, and "you can tell them anything, provided you say it right. They are always ready to listen."

The old mode of diplomatic interaction and cocktail networking on small, intimate levels has given way to mega-events with hundreds of people seated in huge ballrooms listening to well-written speeches. "The sociology has changed," Bujon mused, from the time his first boss at the French foreign service, Herve Alphand, served as ambassador here from 1956 to 1965. In his memoir, "The Amazement of Being," Alphand describes his close friendship with then-Sen. John F. Kennedy and small dinners in which a columnist or two, a senator or two, and a great tycoon passing through town actually did business in the home of a Georgetown socialite.

Bujon has visited 44 American states and regrets not having been to the remaining six. He also laments not having spent enough time with his friends, enjoying the many cultural outlets and activities available, or cracking the hundreds of books he meant to read. "That's Washington; an ambassador's life is always busy and great fun. You can't draw a line between your professional and public life, but there is so much diversity," he remarked with satisfaction.

Bujon is "walking into the sunrise," not the sunset, he pointed out, as he prepares to revive his private company, a consulting firm catering to CEOs on political strategy and risk analysis, and embarks on a new position (to be announced in January) with "transatlantic" responsibilities.

His tenure here will be unforgettable for the variety of experiences and insights it has offered him, "like a constantly changing kaleidoscope" with its varied seasons, stream of visitors and window on the rest of the world. "I will miss that, and several generations of friends I have made here," he concluded.

Outgoing Ambassador Francois Bujon de l'Estang said that because France is a true friend, "we speak up when we differ in our judgment."