Klestil, 71, died Tuesday of multiple organ failure, just two days before the end of his second six-year term.
Four days of mourning began with Klestil's casket arriving Wednesday at the presidential office in Vienna. Thousands of people were expected to file past the casket, which was draped with the Austrian flag and flanked by military honor guards, to pay their final respects.
A memorial service open to the public was to be held Friday in a chapel in the Hofburg, the imperial palace in central Vienna where the presidency is based. Klestil was to be laid to rest Saturday in a state funeral at Vienna's Central Cemetery following a requiem Mass at St. Stephen's Cathedral, the Austria Press Agency said.
Condolences came in from around the world for a leader praised for improving Austria's standing in the world and for developing relations with emerging Eastern European nations.
Russian President Vladimir Putin called Klestil "an outstanding Austrian statesman, a politician with great international authority, and a consistent proponent of the development of friendly ties of partnership between our countries."
German Chancellor Gerhard Schroeder expressed "deep sorrow" at Klestil's death. "Austria has lost a statesman, Germany a friend and Europe a bridge-builder," Schroeder wrote.
Italian President Carlo Azeglio Ciampi recalled how "the lucidity of his political mind and an extraordinary human strength distinguished a person who I was linked to by genuine friendship."
Their words of praise were echoed by Austrian Chancellor Wolfgang Schuessel, who took over the presidency earlier this week when Klestil fell ill. "Austria lost a great personality, a committed Austrian and European, who had dedicated his life to serve his country and its people," he said.
Klestil also was credited with helping to distance Austria from its Nazi past after years of controversy over his predecessor Kurt Waldheim's World War II service in the German army. Klestil's first term included a visit to Israel, where he expressed sympathy for Holocaust victims.
"President Klestil was a man of honor and a man of word whose personal integrity and openness helped rebuild relations with the United States and the Jewish world following the controversy surrounding the WWII record of his predecessor Kurt Waldheim," said Rabbi Abraham Cooper, associate dean of the U.S.-based Wiesenthal Center.
Critics occasionally accused Klestil of overstepping the ceremonial bounds of his office. But he proved an efficient president, and in 1995, during his first term, Austria joined the European Union.
When the European Union punished Austria for allowing the rightist Freedom Party to join the government, Klestil put his diplomatic skills to work and lobbied heads of states to lift sanctions seven months after they were slapped on the nation.
The Viennese-born Klestil studied economics and business and earned a doctorate in 1957. He worked for the Paris-based Organization for Economic Cooperation and Development before becoming a diplomat.
In 1969, he established the Austrian General Consulate in Los Angeles, where he befriended Arnold Schwarzenegger, the Austrian bodybuilder who went on to become a movie star and is now the governor of California.
In 1978, he was appointed Austria's ambassador to the United Nations. Four years later, he moved to Washington, where he became the Alpine nation's ambassador to the United States.
Klestil moved back to Austria in 1987 to serve as secretary-general for foreign affairs, becoming the highest-ranking career diplomat in the Foreign Ministry.
He was elected president in 1992, succeeding Waldheim, and was re-elected in 1998.
Heinz Fischer, who was chosen in elections earlier this year as Austria's next president, takes over the job on Thursday.
While the post is mostly ceremonial, Austria's president is commander in chief of the country's military, and the constitution gives the head of state the power to reject nominations for Cabinet ministers or even to remove them from office — something that has rarely been done.
Klestil was airlifted to the hospital Monday in critical condition after suffering heart failure. He had suffered from ill heath in recent years.
In 1996 he contracted a severe case of pneumonia and suffered a lung embolism a few months later. Earlier this year, he had surgery on both of his Achilles tendons after injuring them during a fall.