Japanese bankers are puzzled by the latest twist in the still-pending U.S.

financial fair-trade bill, but few analysts or industry sources believe its proposed penalties would have much initial impact even if they were to be enforced.

The bill, aimed primarily at Japan, passed two U.S. House banking panels last week and would give U.S. regulators the power to retaliate against foreign banks if their home markets were found to discriminate against U.S. banks - or car makers.Major city bank planners and Ministry of Finance regulators dismiss that final provision as an obvious, if unexpected, political ploy.

The provision about car makers "is so weird that I'm not sure if we should be worried about it or not," said an official at the finance ministry's International Finance Bureau, who has closely followed the development of the financial fair-trade bill.

"I have more faith in the intelligence of U.S. lawmakers than to think they will pass the bill as it stands," said a manager of U.S. operations for one of Japan's largest city banks, who like others asked not to be identified.

"It's ridiculous," he said.

The ministry continues to voice its opposition to the bill in communications with U.S. Treasury officials, said the Finance Bureau official.

''We are gravely concerned . . . Japan is obviously the single target," he said.

But Japanese bankers said the bill's penalties - potential restrictions on new asset growth or limits on new business - would have little impact if they were implemented now.

Because of a growing share of bad domestic loans and a continuing pinch in meeting capital-adequacy standards set by the Bank for International Settlements (BIS), major Japanese banks have put the brakes on U.S. expansion anyway, they said.

"It would be shameful if the bill were passed. But even if Japanese banks are the target of retaliation, we would be rather happy now to give up expanding our business in the US because we are retreating from there anyway," said an international planning officer at another of Japan's largest city banks.

Officials and analysts dispute the contention that U.S. banks operating in Japan are treated unfairly, arguing they in fact enjoy some privileges not open to their domestic competitors like the ministry's sanction to operate both securities subsidiaries and trust operations.

"The reality is few U.S. banks here are complaining. The bill is just a political tool," said a planning officer at another Tokyo-based city bank.

Of the 20 U.S. banks with Japanese branches in fiscal 1990-91, the last year for which statistics are available, 11 reported losses.

But Yushiro Ikuyo, a financial analyst at Lehman Brothers Japan, and other analysts blame the foreign banks' concentration on unprofitable lines of business, not structural barriers, for that weak performance.

"They have put their main stress on (wholesale banking) . . . Where even Japanese banks can't make both ends meet," Mr. Ikuyo said.

Nozomu Kunishige, a banking analyst at Kleinwort Benson International, said the U.S. bill's penalties, if ever imposed, could most damage Japanese banks with long-term plans to move into securities businesses in the United States.

The Long-Term Credit Bank, Industrial Bank of Japan, Mitsui Taiyo Kobe and Mitsubishi Trust have all expressed interest in acquiring futures or securities subsidiaries in the United States, he said.

"But for a short time at least, the penalty would not have a big impact," Mr. Kunishige said.

The first city bank official agreed: "This is a rough time when you concentrate on your core business. . . . But when this passes, people will start to look at new businesses again."