NEW YORK, AUG. 26 -- The dollar closed slightly lower today in moderately active trading after it failed to sustain an early advance on supportive comments from American and Japanese central bank officials.

Gold was little changed.

In New York, the dollar slipped to 142.90 yen, down from Tuesday's close of 143.50. Overnight in Tokyo, the dollar closed at 142.95, up 0.05 yen from the previous close of 142.90.

Bank of Japan Governor Satoshi Sumita said the central bank would intervene when necessary to stabilize exchange rates. However, he declined to give details of the bank's dollar-buying efforts in recent days.

Sumita also said there had been no departure from the agreement among the major industrial nations to keep exchange rates stable.

Thomas Benfer, a trader with the Bank of Montreal in New York, said the dollar was unable to sustain its intraday high of 1.8333 against the West German mark, reached shortly after Federal Reserve Governor Robert Heller said he would prefer to see no further decline in the dollar. Heller made his comments in Austria.

Heller's "comments pushed it up in the morning," Benfer said, "but it tended to tail off throughout the rest of the day."

Against the West German mark, the dollar ended at 1.8267, down from 1.8300. Earlier in Frankfurt, the dollar rose to 1.8267, up from 1.8205 on Tuesday.

"Whenever there is any news to push the dollar up, anything bullish, the dollar is unable to maintain those levels," Benfer said. "The market is still trying to look for ways to sell the dollar."

Benfer said the Bank of Japan seems to be "saying the next time they come into the market they are going to coordinate with other central banks.

"It does seem like the central banks are going to make a stand if we test the lower levels," Benfer said. "The market would like to go to those levels to test the resolve of the central banks."

Benfer placed the lower levels at 1.80 mark-1.81 mark and 140 yen.

In London, the pound slipped to $1.6175, down from $1.6185. Later in New York, the pound fell slightly to $1.6165, down from $1.6169 Tuesday.

The dollar rose to $1.3217 Canadian dollar from $1.3106.

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

Zurich, 1.5040 Swiss francs, up from 1.5015 (1.5060 vs. 1.5062); Paris, 6.1070 French francs, up from 6.0855 (6.0995 vs. 6.1115); Milan, 1,322.40 lire, up from 1,318.30 (1,322.50 vs. 1,324); Amsterdam, 2.0580 guilders, up from 2.0430 (2.0585 vs. 2.0605).

Republic National Bank in New York closed cash gold at $457.25 an ounce, down slightly from its Tuesday close of $457.50. New York's Commodity Exchange settled the spot contract at $457.30, up from $457.

In Zurich, gold closed unchanged at $458 an ounce. In London, it ended at $457.75, down from $458.25.

Silver rose to $7.71 an ounce from $7.69 on the cash market; the Comex settled it at $7.715, up from $7.682. Earlier in London, silver closed unchanged at $7.74