A written Chinese pledge to forswear new nuclear dealings with Iran cleared the way for President Clinton to say yesterday that he will approve exports to China of advanced U.S. nuclear technology in a deal that will likely be closely scrutinized and vigorously debated on Capitol Hill and among private groups that follow U.S.-China relations.

The new Chinese pledge was made in a confidential letter to Secretary of State Madeleine K. Albright last week by Foreign Minister Qian Qichen, which U.S. officials promised to show privately to designated members of Congress. It specifically commits China to provide no further nuclear assistance to Iran, a country that Washington alleges has been trying to build a nuclear bomb.

China had long resisted making a pledge that specifically mentioned its relationship with Iran, a fellow nonaligned country that is likely to become a major oil supplier as China's energy shortage grows more acute during the coming decade. But Beijing finally agreed to list Iran after Clinton told a senior Chinese national security official, Liu Huaqiu, in Washington two weeks ago that it was a nonnegotiable condition for a deal.

The subsequent agreement was billed by officials as the most important of those sealed at yesterday's summit between Clinton and Chinese President Jiang Zemin, although the two leaders also agreed to establish a communications hot line, begin new cooperation in fighting narcotics and international crime, and work out a way of avoiding accidents between military ships at sea.

Officials said the president's decision to give China something it badly wants -- access to U.S. nuclear technology -- in exchange for gaining a clear-cut Chinese concession only on its worrisome commerce with Iran reflected a strategic calculation that China was unlikely to make similar concessions on any other matters of contention between Washington and Beijing.

U.S. unhappiness with China's policies on trade and human rights never even figured in the bargaining, the officials said, due to U.S. concerns that China would balk and angrily make its nuclear technology purchases elsewhere if Washington made the price for a deal too high. "To pile a number of other conditions on top of that would have been to move the goal posts," said one official. "It was not appropriate."

The agreement does not require China to cancel two existing nuclear-related projects in Iran, to construct a small research reactor and a factory to manufacture a special metal sheath -- known as zirconium cladding -- for nuclear fuel rods that would be used in a larger nuclear reactor. But U.S. officials said that neither of these poses any risk of helping Iran build a nuclear bomb and that both will be finished within a few years.

The elevation of U.S. concerns about China's dealings with Iran above all other contentious topics in U.S.-China relations stemmed in part from the administration's abiding concern that the development of nuclear arms in Iran would be disastrous for the Middle East and for U.S. security. Washington has long taken the position that assistance to any civilian nuclear power program there would help transfer know-how that could eventually be used to make bombs.

But the administration's decision also had its roots in legislation initially passed by Congress 12 years ago and refined in 1990, which posed only a single substantive condition for allowing China to buy U.S. nuclear reactors worth billions of dollars: It demanded that China halt its assistance to foreign nuclear weapons programs. The legislation grew out of a widespread conviction on Capitol Hill that China had been dishonest when it promised not to contribute to nuclear proliferation at the same time it was providing covert nuclear assistance to Pakistan and Algeria.

Congressional critics of China's behavior had called for the administration to impose additional conditions, including gaining new assurances that Beijing will sell no more cruise missiles to Iran, end its transfers to Iran and other nations of chemical weapons and missile-related technology, and will no longer sell nuclear reactor gear to India and Pakistan until both countries agree to allow international monitoring of all their nuclear facilities.

But U.S. officials conceded this week that China had flatly rejected the third demand and provided assurances on the first two that fell short of what they considered completely clear-cut. These items were, as one official said, "a lesser priority . . . {and} not critical for this summit," so the officials resolved to put off their resolution until later. CAPTION: SUMMIT ACCORDS President Clinton's certification yesterday that China is not exporting nuclear technology for weapons development puts into effect a 1985 agreement allowing the U.S. nuclear industry to sell reactors and technology in China. Clinton and Jiang Zemin also pledged to: - Hold regular strategic meetings at every level of governments. Clinton plans to go to China next year. - Establish a hot line to provide a direct communications link between the presidents. - Increase U.S. support of China's developing legal system, including training lawyers, prosecutors and judges. - Step up anti-drug, anti-crime cooperation, including allowing the United States to open a Drug Enforcement Agency office in Beijing. - Accept a Military Maritime Cooperation Agreement to handle incidents at sea by establishing closer communications and rules for when the nations' ships and submarines encounter one another. - Sign a deal today between the Chinese and Boeing Co. to buy 50 airplanes for $3 billion. SOURCE: Associated Press CAPTION: The Chinese first couple meet U.S. counterparts on arrival at the White House.