Venezuela lowered its heavy crude oil prices by $3 per barrel yesterday, following an agreement by Venezuela and Mexico to cut prices together.

Mexico slashed the export price for crude oil by an average of $4 per barrel Friday after a two-day meeting of their presidents.

Mexican President Miguel de la Madrid and Venezuelan President Jaime Lusinchi held the meeting to reestablish the close cooperation Latin America's biggest oil producers had until last year, when Mexico unilaterally cut its prices, forcing Venezuela to follow suit. Mexico has reduced prices three times since then, requiring Venezuela to match its price cut each time.

Following their get-together, Lusinchi and de la Madrid called for an urgent meeting of Latin American debtors to stave off a foreign debt crisis caused by the falling oil prices. The so-called Cartagena Group -- named after the Colombian city at which the nations originally met -- has not met since last year.

Today, Colombian President Belisario Betancur, whose nation has a $14 billion foreign debt, called for the meeting to be held "as soon as possible," according to the Venezuelan government news service.

The coordinated price reductions indicate that Mexico, which is not a member of the Organization of Petroleum Exporting Countries, is willing to cooperate with Venezuela, a charter member of OPEC.

A five-nation OPEC committee is scheduled to meet Monday in Vienna to seek ways to prevent prices from falling even more. Venezuela's oil minister, Arturo Hernandez Grisanti, is OPEC's chairman.

Venezuela's price cut, retroactive to Jan. 27, affects approximately 500,000 barrels per day of the country's heavy crude export, said Deputy Energy and Mines Minister Hernan Anzola. Heavy crude accounts for 45 percent of Venezuelan oil exports.

"This [price] adjustment makes us competitive with Mexican heavy crude in our main export market, the United States," Anzola said.

The price cut will cost Venezuela $475 million this year, Anzola said, putting oil income below the $12.6 billion target level. Oil exports earned $14.8 billion in 1985.

Despite efforts to diversify the economy in the past two years, oil still accounts for 90 percent of export earnings, 60 percent of government revenue and 25 percent of gross national product.

Venezuela is in better shape than Mexico, which is warning it cannot come up with interest payments on its $97 billion foreign debt because of the loss of oil income.

Venezuelan officials and foreign bankers here said they will sign an agreement rescheduling $21.2 billion of the country's public sector foreign debt as planned on Feb. 26.