THE fast-rising yen may be the only thing strong enough to make Japan think the previously unthinkable: setting a ''numerical target'' to reduce its huge trade surplus.
Up to now, Japan has derided such an idea as ''managed trade,'' as opposed to free trade. And it has rejected requests by the Clinton administration to set ''objective criteria'' to measure progress on agreements to open Japanese markets to foreign goods. Tokyo officials have preferred vague agreements.
But on April 11, Prime Minister Tomiichi Murayama acknowledged that some members of his ruling coalition are urging a fixed goal for narrowing the trade imbalance. ''We have been considering many things and should take bold measures,'' he said.
With the Japanese currency now buying 20 percent more dollars than it did at the beginning of this year, political leaders have been huddling to come up with ways to bring down the yen. It hit a postwar record of 80 to the US dollar on April 10, making Japanese exports ever more expensive and threatening to send the economy back into recession.
In the view of many economists, the trade surplus is the key factor driving up the yen. Last year, the surplus exceeded $130 billion, with about half of that with the US. Japanese exporters must buy yen to bring their overseas profits home.
While the prime minister described the idea of a target as ''difficult,'' at least one senior politician said it was ''necessary'' for the government to announce its intention to cut the surplus by a specific amount.
The surplus ''is one of the fundamental reasons for the upward trend of the yen,'' said Koji Omi, the chairman of the Japanese parliament's finance committee.
He said members of his Liberal Democratic Party (LDP), the majority member of Murayama's government coalition, were trying to build up a political consensus in favor of cutting the trade gap in half, perhaps in three to five years. ''I think it's necessary,'' he added.
Perhaps more significant is the high-level acknowledgment that the trade surplus is playing a key role in pushing up the yen. The government usually blames speculators for the global currency crisis.
United States diplomats in Tokyo have been following the hints about ''numerical targets,'' but nobody is chortling yet.
''That's an interesting change,'' says one US official here, speaking on condition of anonymity. But he adds: ''What is needed [on April 14, when the Japanese government is set to announce measures to stem the yen's rise] is a policy statement. Setting a goal for the surplus is not a policy, it's a goal, and it begs the question of how they will achieve it.''
It may be that Japanese officials are trying to impress international currency markets, which have been resolutely unimpressed with Japan's existing attempts to curb its currency's growing strength. The LDP may also have a political reason for promoting the announcement of a surplus-reducing target.
Local elections over the weekend demonstrated that Japanese voters are thoroughly disenchanted with established political parties, and the LDP may be trying to look assertive in advance of an important set of parliamentary elections this July.
As Mr. Omi notes, Japanese officials are also realizing that they must take the lead in reversing the yen's rise and the concomitant fall in the value of the dollar. The US government is ''not interested in defending the dollar's value as long as the economy of the US is going well,'' he observes.
He also rejects the current strategy of US trade officials, who have been concentrating on opening particular sectors of the Japanese economy, such as the auto-parts market. Omi says Japan should announce a target and implement macroeconomic measures to make it happen, such as a fiscal-stimulus package that would enliven the economy and boost imports.
The most vociferous opponents of any public agreement to reduce the trade gap by a fixed amount have been Japan's powerful bureaucrats, who worry that other governments could use the failure to achieve such a goal as a justification for trade sanctions.
One senior bureaucrat refused to believe a word of Murayama's comments. ''I don't think [the prime minister made such hints],'' said Takeshi Saito, deputy director of the Americas Division of the Ministry of International Trade and Industry (MITI). ''He knows the arguments against numerical targets very, very well.''
''My ministry is strongly against numerical targets,'' he added. ''Our position is very, very decided.''