WASHINGTON (Reuters) - U.S. tomato growers on Monday said they have formally asked the U.S. Commerce Department to tear up a pricing agreement with Mexican producers that they say has become "a charade."

Reggie Brown, executive vice president of the Florida Tomato Exchange, told Reuters U.S. producers want the pact voided so they can file a new anti-dumping complaint against Mexico.

The rare request comes in a dispute that dates back to 1996, when U.S. industry filed a petition accusing Mexican producers of selling in the United States at unfairly low prices.

Brown said the Commerce Department found that Mexican producers were dumping their tomatoes in the United States at nearly 188.5 percent below fair market value.

The department later agreed to suspend action on the petition and negotiate a "suspension" agreement with Mexican producers and exporters that established a minimum reference price for Mexican tomatoes in the United States.

In following years, two more suspension agreements were negotiated to replace the original pact, but the reference price barely changed, Brown said.

In the meantime, U.S. tomato imports from Mexico nearly tripled in value to about $1.8 billion last year.

"Over this entire period U.S. growers have been the victims of gamesmanship and evasive actions by Mexican growers," Jimmy Grainger, president of the Florida Tomato Exchange, said in a statement.

"It's time to end the charade and restore fair prices that reflect market reality", he said.

The U.S. industry feels the best way to do that is to ask to withdraw its original petition and thereby terminate the current suspension agreement, so it can file a new case, Brown said.