Nine Latin American countries condemned today Friday's Mexican-French recognition of El Salvador's leftist opposition forces, further escalating a diplomatic battle between supporters of the U.S.-backed government there and the guerrillas trying to overthrow it.

A joint statement issued in Caracas, Venezuela, was signed by the foreign ministers of Argentina, Bolivia, Colombia, Chile, Guatemala, Honduras, the Dominican Republic, Paraguay and Venezuela.

The document accuses "two friendly governments," France and Mexico, of deciding to "interfere in the internal affairs of El Salvador" by issuing a declaration "tending to favor one of the subversive extremes that operate" in El Salvador in an "armed struggle for the conquest of the government."

The joint Mexican-French statement on Friday recognized the guerrillas and their political allies as a "representative political force" which should be included in a negotiated solution to the Salvadoran civil war.

Norway, Nicaragua and Cuba reportedly have hailed the Mexican-French initiative as a proper move toward peace in the region.

El Salvador's Foreign Ministry has issued notes of protest to both France and Mexico, while Venezuela has recalled its ambassadors from those countries for consultations. A meeting of the presidents of Mexico and Guatemala, scheduled for Saturday, has been postponed indefinitely.

Ever since El Salvador's social and political unrest began to expand toward full-scale civil war more than a year ago, the diplomatic front has been almost as important to the antagonists as the actual fighting.

The United States has tried to portray the Salvadoran war as a proxy confrontation between Washington and the Soviet Union, which the Reagan administration says supports the guerrillas with advice and arms. But the diplomatic battle lines now emerging are much more complex than that.

The United States and to a lesser extent Venezuela have consistently backed El Salvador's coalition government of military officers and Christian Democratic politicians. At the same time, however, El Salvador's Social Democrats and the leftist wing of the Christian Democratic Party allied themselves with the Marxist-led insurgents through the Democratic Revolutionary Front.

A central element in the argument is just what constitutes "outside intervention" in El Salvador, with the United States saying that the guerrillas are maintained and supported by outside powers while the insurgents' diplomatic supporters point to the more obvious military and economic aid being given by Washington to El Salvador.

Both the Salvadoran government's civilian representatives and the dissident Christian Democrats in the Revolutionary Front have tried to enlist other Christian Democratic parties in their causes. Social Democrats in the front have traveled throughout Latin America and to Europe. The Socialist victory in France gave the front a tremendous European impetus, culminating in Friday's declaration.

At the same time, Mexico's ruling Institutional Revolutionary Party has offered the guerrillas a base of political and diplomatic operations here while more and more openly favoring their cause in El Salvador.

Antagonism to the Mexican-French initiative on the part of Guatemala, which denounced it independently, as well as Uruguay, Chile, Argentina and Paraguay was easy to predict, as were plaudits for the move on the part of communist Cuba and leftist Nicaragua.

But in Venezuela particularly, which has emerged as the Salvadoran government's second-strongest backer after the United States, the Salvadoran war is also the focus of longstanding internal political debate. The previous Social Democratic government of Carlos Andres Perez had aided Nicaragua's Sandinistas in their war against the Somoza dictatorship, but Caracas' present Christian Democratic President Luis Herrera Campins has sided with the Duarte government against the Salvadoran insurgents.

Colombia's position in the debate is complicated. Its government has steadily warmed to the Reagan administration, suspending relations with Cuba after charges that Cuba had trained Colombian guerrillas, and sending troops to the Sinai peacekeeping force.