Richard Nixon had a sensitive item on his agenda as he began reaching out to China in the spring of 1971: the release of four Americans held by the communist government. 

Like President Bush in the current standoff, Nixon and his advisers did not want to provoke the Chinese. They knew that only deft handling of the issue might secure the release of the four, including two pilots on a spy mission who were shot down during the Korean War nearly 20 years earlier. 

In today's diplomatic impasse, Bush has said China must release 24 Americans who were on a U.S. spy plane that collided last weekend with a Chinese fighter jet and made an emergency landing on China's Hainan island, where they are being held. 

Months before Nixon's historic trip to China in February 1972, his national security adviser, Henry Kissinger, took a nonconfrontational approach, asking the Chinese to free the four men as a favor on humanitarian grounds. 

"We would consider it an act of mercy if the People's Republic of China could pardon all or some of them whenever, in its judgment, it felt that conditions were right," according to a transcript of Kissinger's meeting with former Chinese premier Chou En-lai in July 1971. "This is not a request. I'm asking it as a favor." 

Chou was noncommittal, but noted that a reduction of a sentence was possible in cases of good behavior. "We shall continue to study this matter." 

Among the detainees was John T. Downey, who was shot down during the Korean War on Nov. 29, 1952. 

"Downey is a confessed spy, and the PRC (People's Republic of China) has been very lenient in commuting his life sentence to five more years," an undated briefing memo on the China trip said about Downey, who was released in March 1973, 13 months after Nixon's visit to China. 

Downey was released after Nixon admitted he was on a CIA spy operation. For years, the State Department had insisted Downey had no ties to the agency. 

Nixon also was concerned about Maj. Philip Smith, whose F-104 jet fighter was shot down in the Gulf of Tonkin in September 1965 as part of U.S. involvement in the Vietnam War. 

Smith, who spent 7 1/2 years as a prisoner of war in China, was initially held on the Chinese island of Hainan. 

The documents were among 100,000 papers made public Thursday that shed light on foreign policy issues facing the Nixon White House, including the Vietnam War, Nixon's trip to China and his summit in Moscow in May 1972. 

Buried in boxes of papers, some yellowed from age, are handwritten notes from Nixon and Kissinger, who jointly arranged the China trip — a bold step in foreign relations. Nixon dispatched Kissinger to Beijing twice to talk to the Chinese before he made his historic visit, which eventually led to renewed diplomatic relations with the communist power. 

Kissinger's first trip, in July 1971, was shrouded in secrecy. He slipped off to China at the end of an Asian tour. In a surprise announcement on July 15, 1971, Nixon told the world about Kissinger's visit and how he planned to formally open dialogue with China in his own trip there months later. 

In a July 14, 1971 memo to Nixon, Kissinger called his first talks with the Chinese — more than 20 hours over two days — the "most searching, sweeping and significant discussions I have ever had in government." 

He told Nixon there were challenges, however, in dealing effectively with the Chinese whom he described as a "tough, idealistic, fanatical, single-minded and remarkable people." Success in relations, he wrote, would "transform the very framework of global relationships." 

The talks were so intense at times that once at lunch, Chou stopped Kissinger and said "the duck would get cold if we did not eat first," the memo to Nixon said. 

But Kissinger said he found negotiating with the Chinese more agreeable than talking with the Russians. "There was none of the Russian ploymanship, scoring points, rigidity, or bullying," Kissinger said. "They did not turn everything into a contest." 

Kissinger's second trip to China, in October 1971, began with a chilly welcome. Upon arriving in Shanghai, Kissinger and his colleagues found in their rooms a "an English-language propaganda bulletin carrying an appeal on the cover for the people of the world to `Overthrow the American imperialists and their running dogs."' 

The American visitors collected the bulletins, presented them to the Chinese, who "received them in silence," Kissinger wrote in a memo dated Oct. 29, 1971. 

But Chinese-American relations were warming in anticipation of Nixon becoming the first U.S. president to visit China. During the visit, Chou and Kissinger sipped green tea in the Great Hall of the People. At a banquet, Chou gave a warm toast and clinked glasses with each American in the room. 

Four months later, on Feb. 21, 1972, Nixon landed in China.