Two of the United States' major entertainment companies are involved in separate deals involving over $1 billion for their sale to foreign owners. They are United Artists movie studio and MCA, the giant conglomerate that owns Universal Studios.

United Artists, maker of Oscar-winning "Rain Man," will be sold to Qintex Group, an Australian entertainment company, for $1 billion under an agreement announced late Friday. The MGM-UA deal would mark the first time a major studio passed into predominantly foreign ownership. .Qintex, one of the makers of the recent CBS miniseries "Lonesome Dove," would get most of the assets of MGM-UA Communications Co., including rights to "Rain Man." Also included would be a library of 4,000 movies, among them the "James Bond" and "Pink Panther" series, the video library and movie and television production and distribution facilities.

In another development, officials of Japan's giant Sony Corp. were reported to be in discussions with executives of MCA to put "final touches" on a deal to acquire the conglomerate that owns Universal Studios.

KNX-AM News Radio, a CBS affiliate, reported that executives of the two giant firms were meeting in downtown Los Angeles to complete the agreement. The station cited unidentified sources. An employee in the office of MCA President Sidney Sheinberg declined to comment on the reported talks and pending deal.

The announcement of the MGM-UA sale said that the company's majority shareholder, Kirk Kerkorian, would retain control of the MGM name and TV and movie studios as well as 34 MGM movies, including "Moonstruck" and "A Fish Called Wanda."

The agreement between Qintex and Kirk Kerkorian is subject to unspecified government, shareholder and "third-party" approvals, according to the joint announcement.

MGM-UA officials refused to elaborate on a news release, which said the deal was expected to be complete in late summer.

It is the second time this year Kerkorian has agreed to sell part of the company he assembled out of the former United Artists and Metro-Goldwyn-Mayer studios.

Kerkorian, who owns 82 percent of MGM-UA through his Tracinda Corp., pumped $180 million of his own funds into the money-losing company in January. MGM-UA lost $39.5 million in the first quarter of 1989 and $48.7 million in 1988.

Under the complicated agreement with Qintex, Kerkorian will hang onto rights to the MGM name and roaring lion logo as well as movie and TV production units. Also remaining with MGM are 34 movies made since June 1986, including "Moonstruck," "A Fish Called Wanda," and "Willow"; 1,750 hours of TV programming including the ongoing shows "thirtysomething" and "In the Heat of the Night"; and the MGM headquarters building here.

The deal is to work this way: Kerkorian sells 100 percent of MGM-UA to Qintex for $20 a share, or about $1 billion. Then the company is split, and Kerkorian buys back what will be the new MGM - the MGM movie and TV studios plus the 34 movies in the MGM film and video libraries - for $250 million.

The Australian company operates in this country as Qintex Entertainment Inc., a TV production company that financed part of the recent CBS miniseries "Lonesome Dove."