Intelsat's top executive is asserting that the United States could be expelled from the global satellite communications consortium if it allows private competition to Intelsat over the organization's objections.

With 109 member nations, Intelsat operates a satellite network that carries roughly two-thirds of the world's international telephone traffic and practically all of the international television transmissions.

Both government officials and industry experts dismiss the possibility of Intelsat expelling the United States as "silly." The United States is responsible for more than a third of Intelsat's telecommunications traffic and revenue. The loss of the United States from Intelsat might make it economically impossible for the organization to survive.

Nevertheless, memos from Richard Colino, Intelsat's director general, contending that the United States could be stripped of its membership reflect the frustration felt at Intelsat over the specter of potential competition.

Colino's memoranda, filed with the Federal Communications Commission, recommend criteria for Intelsat approval that would make it unlikely that private satellite network competition would be economically feasible.

The memos were sent to the consortium's board of governors in anticipation of a meeting next Wednesday.

They have infuriated Commerce Department, State Department and FCC officials who are now considering applications from several American companies that want to offer private international satellite services.

"I'm very concerned about the latest proposed changes in Intelsat rules that will be submitted to Intelsat's board of governors," said a top Commerce Department official who asked not to be identified. "They would preclude an administration policy position regarding something we consider to be very important."

The official says that the Communications Satellite Corp. (Comsat), the U.S. signatory to the Intelsat Agreements, will be instructed to try to defeat or delay the proposals.

Comsat owns roughly 23 percent of Intelsat and is the major user of the consortium's global satellite network.

"This hits suddenly without giving us the time to study a set of major proposals by the Intelsat staff," says a government telecommunications official. "Some would say if the proposals were adopted, it would be almost impossible to have separate international satellite systems. We are concerned about this. We don't know what's motivating Intelsat to take these steps."

Intelsat has said that competitive international satellite networks would jeopardize the organization's existence and would violate the Intelsat treaties, which state that other international satellite efforts must be coordinated with Intelsat. Members of less-developed nations fear that their rates could go up if Intelsat loses business to private satellite carriers.

The crux of Intelsat's concern is the serious consideration the Reagan administration is giving to several applications by U.S. companies, including Orion Satellite Corp. and International Satellite Inc., to launch rival services. These applications have been pending for more than a year.

"Intelsat wants to be an absolute monopolist," said Tom McKnight, Orion's president. "They're really nothing more than a back-office switching system."

Observers speculate that Colino has chosen to display publicly his unhappiness with this administration's international telecommunications policies. An Intelsat spokeswoman said Colino was unavailable for comment.

Government sources, who generally credit Colino for his political skill, believe this effort has hurt his position with the administration.

"I think it just backs us into a corner," says the Commerce official, "and we don't like that. We're going to make sure [Comsat] opposes it."