Gold and silver futures soared Monday to their strongest levels in more than two decades, boosted by geopolitical concerns and a sharply softer U.S. dollar.

The most-active June gold contract hit a contract high of $619.30 an ounce on the New York Mercantile Exchange, its strongest level since December 1980. June gold settled up $18.70 at $618.80 an ounce.

April gold settled up $18.90 at $615.40 an ounce, after hitting a high of $616.50.

Meanwhile Monday, May silver peaked at $13.38 an ounce, the metal's strongest level since 1983. It settled up 51 cents at $13.365 an ounce.

"There are increased geopolitical tensions, mainly from Iran," said Peter Grandich, a gold analyst and publisher of the Grandich Letter. "Also, the topping of the U.S. dollar is now evident."

Several traders cited ongoing concerns about Iran's nuclear program and concerns about whether the United States would launch an attack. Iran has said it would go ahead with plans to enrich uranium, defying the United States, Europe and United Nations nuclear experts. Iran has said its nuclear ambitions are peaceful, but Western countries fears it plans to arm itself with nuclear weapons.

George Gero, vice president with RBC Capital Markets Global Futures, said higher energy prices contributed to gold's rise, along with Iran-related worries and the weakening dollar.

May crude futures on Nymex rose more than a dollar Monday to settle at a record high of $70.40 a barrel.

The dollar tumbled after reports that China could reduce its buying of U.S. Treasury products. There was also speculation that the Federal Reserve may finish its rate-increase cycle sooner than expected.

As gold was closing Monday, the euro had risen to $1.2269 from $1.2110 late Friday. A weaker dollar tends to push gold higher because gold, denominated in the dollar, is regarded as an alternative investment to the U.S. currency.

Volume was robust in metals trading Monday, with some 25,000 silver trades and 60,000 gold trades, Gero said. He added that there was a "tremendous" amount of short covering, or buying by traders to offset positions in which they had previously sold.

"New funds were coming in," he said. "And there were the momentum players who always buy new highs in heavy volume."

However, Grandich and Gero both cautioned that gold is reaching such lofty levels that the market could be prone to some kind of correction lower.

"When everything looks so bullish, an unexpected sale by a central bank or an unexpected political event could have a lot of the weak holders in the market wanting to exit," Gero said.