NEW YORK, AUG. 10 -- The dollar declined slightly against major currencies today in a move described by one dealer as significant only because it was the dollar's first sign of weakness in trading this months.

Manufacturers Hanover Trust Vice President James Vick called today a day of "round trip" trading, containing an upswing in the morning, an early afternoon decline, and a close back near the opening level.

Gold and silver, meanwhile, both moved higher.

In New York, the dollar dipped slightly to 1.8920 West German marks, from 1.8930 on Friday. Earlier in Frankfurt, the dollar ended at 1.89 marks, up slightly from a Friday close of 1.8822.

The dollar ended at 151.00 Japanese yen in late New York trading, down from Friday's close of 151.75. Overnight in Tokyo, the dollar rose to 151.45 yen, up 0.22 yen from the previous close of 151.23 yen.

Vick said the dollar's morning rise in New York coincided with reports that another tanker had struck a mine in the Persian Gulf.

He said the dollar weakened at midday, about the time of press reports that the Bundesbank and the Federal Reserve had intervened.

However, Vick said he was not certain the dollar's movements were strongly linked to these events, pointing out that the press reports did not spark much discussion in New York's money markets.

"There really wasn't a big change today," Vick said. "The only real news is that the dollar weakened at all."

In London, the pound rose to $1.5680, up a bit from $1.5655. In New York, the pound finished at $1.5690, up slightly from $1.5640 Friday.

The dollar increased fractionally to $1.3280 Canadian from $1.3236.

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

Zurich, 1.5755 Swiss francs, up from 1.5730 (1.5730, unchanged); Paris, 6.3200 French francs, up from 6.28 (6.3120 vs. 6.3020); Milan, 1,371.00 lire, up from 1,364.60 (1,391.00 vs. 1,370.50); Amsterdam, 2.3348 guilders, up from 2.1280 (2.1310 vs. 2.1290).

Republic National Bank in New York closed cash gold at $460.75 an ounce, up $6.75 from $454 Friday. New York's Commodity Exchange settled the spot contract at $460.40, up $5.80 from $454.60

In Zurich, gold fell to $459.50 an ounce, from $463.65 on Friday. In London, gold dropped to $458.50 from $463.25

Silver rose to $7.72 an ounce from $7.625 on the cash market; the Comex settled it at $7.727 down from $7.59. Earlier in London, silver weakened to $7.685 from $8.025