Japan appears likely to face strong pressure from the United States within the next few months over a prickly issue that has proved divisive ever since President Bill Clinton took office four years ago: How to deal with Iran.U.S. relations with Iran, which have been tense since the 1979 Islamic Revolution led by Ayatollah Khomeini and the subsequent hostage crisis at the American embassy in Tehran, may reach a boiling point once Clinton begins his second term on Jan. 20, according to Japanese government officials. Depending on developments in the international situation surrounding Iran, Japan may even be forced to abandon its policy of "constructive engagement" and cancel its already-stalled huge loan program, the officials said on condition of anonymity.That would be a humiliating diplomatic setback for Tokyo, which has argued against Washington's policy of "dual containment" against Iran and Iraq. Japan has staunchly advocated pushing for favorable changes through contacts, rather than international ostracism as the U.S. wants. "Japan's policy toward Iran will probably face a critical phase within the next couple of months," one of the officials said.Saudi Arabia is now completing its investigation into the bombing last June of the Khobar Towers American military housing compound in Dhahran, which claimed the lives of 19 U.S. servicemen. If the investigation turns up evidence of Iranian involvement in the bombing, the Clinton administration would not be able to resist pressure at home, especially from the Republican-dominated Congress, to retaliate, possibly even with a direct military strike under its right to self-defense, Japanese government officials and analysts say.