NEW YORK, JULY 7 -- The dollar broke through a key barrier against the Japanese yen today, advancing above the 150-yen level for the first time in 3 1/2 months in the most active session in recent weeks. Gold fell.

Traders attributed the dollar's sharp gain to an overall bullish sentiment -- albeit for the short term -- the testimony of Lt. Col. Oliver North on Capitol Hill and overnight comments by a high-ranking Japanese official.

In New York, the dollar surged to 150.25 yen, up from 148.90, and the highest level since March 23. Earlier in Tokyo, the dollar closed at 149.45, up from Monday's close of 149.25 yen.

"The catalyst today was the testimony by North down in Washington," said Robert Ryan, New York foreign exchange manager at Irving Trust Co., referring to the first public testimony by North in the Iran-contra scandal.

"If he {had} fingered Reagan, that would have been bad politically for the United States and the dollar could have come off," Ryan said. "He shielded Reagan right from the start."

Dealers in Tokyo said the dollar received an early boost on comments from Japanese Finance Minister Kiichi Miyazawa that there was no need for central bank intervention to check the yen's recent fall.

"Obviously, the market seems to think that without intervention the dollar will go higher," said Michael J. Duffy, vice president and chief trader at European American Bank in New York.

In Frankfurt, the dollar closed at 1.8380 marks, down from the previous close of 1.8419. But in New York, the dollar rebounded to close at 1.8425, up from the previous level of 1.8375.

In London, the pound closed at $1.6210, up from Monday's $1.6160. In New York, the pound fell to $1.6190 from $1.6215.

The dollar fell slightly to $1.3230 Canadian from $1.3262.

Other European closing rates with late New York prices and comparable Monday rates in parentheses:

Zurich, 1.5315 Swiss francs, down from 1.5330 (1.5380 versus 1.5335); Paris, 6.1200 French francs, down from 6.1300 (6.1360 versus 6.1320); Amsterdam, 2.0680 guilders, down from 2.0725 (2.0730 versus 2.0700); Milan, 1,331.00 lire, down from 1,333.20 (1,333.00 versus 1,331.00).

In Zurich, gold rose slightly to $444.50 an ounce from $443.50 Monday. In London, gold closed unchanged at $443.

Republic National Bank in New York closed cash gold at $444 an ounce, down from $448.25 Monday. New York's Commodity Exchange settled the spot contract at $443.80, down from $448.

Silver fell to $7.47 an ounce from $7.57 on the cash market; the Comex settled silver at $7.475, down from $7.57. Earlier in London, silver rose to $7.41 from $7.255.