Two days before the Redskins and their star running back, John Riggins, are due to begin negotiations over a new contract, two of the team's other 15 free agents say management appears to be ignoring the existence of the new U.S. Football League.

And yesterday, for the third time, the Redskins did not make free-agent linebacker Rich Milot an offer, as promised, according to Richard Bennett, Milot's attorney. Milot reportedly had received a verbal offer from the USFL's Philadelphia Stars.

"Richard Bennett has told me they (the Stars) made an offer, and I'm not going to be used . . . I'm not going to give him an offer to go out and shop around with," said Redskins General Manager Bobby Beathard. "They want to get it done. We want to get it done. There's a right way and a wrong way, and we have strong feelings about how to do it."

Bennett said he and Beathard had talked and were far apart. "Obviously, the Redskins will be putting Rich Milot in a position which will be very difficult to remain with the Washington Redskins if they don't make an offer."

Bennett said there was no deadline in the negotiations.

Bennett also represents free agents Mike Nelms, all-pro kick returner, and starting middle linebacker Neal Olkewicz. They approached USFL teams but are not negotiating with USFL teams.

In addition to Riggins, Milot, Nelms and Olkewicz, the Redskins' free agents who received qualifying offers from the team are safety Mark Murphy, linebacker Peter Cronan, defensive tackle Darryl Grant, tackle Joe Jacoby, defensive tackle Pat Ogrin, quarterback Tom Owen, safety Tony Peters, cornerback Jeris White, tight end Mike Williams, running back Otis Wonsley and center Jeff Bostic.

"We're pretty far apart right now," said Nelms of an offer he said he got from the Redskins. "I didn't think I'd have that much difficulty to get a pretty good contract. They didn't pay much attention to the new league. They're going about business as usual."

Nelms is one of two of the free agents who have received more than the standard qualifying offers required for the Redskins to receive compensation in case he signs with another team. The other, according to Beathard, is Murphy, the team's player representative.

Beathard said he had talked to some of the other free agents recently and had appointments scheduled with them or their agents this week.

"Time is of the essence. The leverage is minimized after this week," said Wilbur Jackson, who said he recently talked to Beathard and is awaiting an offer.

Only three NFL players who became free agents earlier this month, including Riggins and Milot, are currently negotiating with the new league, according to a USFL official who said the third was not a Redskins player. He said that the 12 USFL teams had been concentrating on the draft and signing draft choices.

Riggins received what two sources say was a three-year, $2.5-million guaranteed offer from the USFL's Michigan Panthers. Redskins' owner Jack Kent Cooke said that Riggins wanted to negotiate last night, but that Beathard was unavailable. Now the meeting, to be held at Cooke's estate in Middleburg, Va., could be today, but more likely will take place Wednesday, according to Beathard.

The USFL season opens Sunday and the Panthers play Monday night at Birmingham. Shire Rothbart, the Panthers' vice president and treasurer, declined comment on substative issues of the negotiations with Riggins.

"He impresses me as a bright, very serious-minded fellow who wants to secure the best deal he can because he's the hottest property in football right now," Rothbart said. "If he turns down the Redskins and we can make a deal satisfactorily, I expect him to be playing for us Monday night. I love it."

Riggins was the team's highest-paid player last season, at $330,000. Quarterback Joe Theismann signed a four-year contract before the 1982 season that will pay him a reported $425,000 in its final year.

The club has a policy against guaranteed contracts.

The Redskins, according to sources, rank in the middle of the league in payroll, about 23 percent lower than the Denver Broncos.

Asked yesterday if he will remain firm on the policy of not giving guarantees, Beathard said, "Yes." According to players' sources, only 5 percent of NFL players have guaranteed contracts. The Chargers have the most, five.

When Riggins sat out the 1980 season, one of the major issues was his seeking guarantees on the final year and option year of his six-year, $1.8 million contract which he signed in 1975. He was one of eight free agents who signed that year when the compensation rule, which the players say restricts free-agent movement, was not in force.

Riggins, the most valuable player in the Redskins' recent Super Bowl victory, told the Panthers' management that he wanted to talk to the Redskins before deciding possibily to become the first big-money defector from the National Football League. The New Jersey Generals of the USFL recently signed Herschel Walker out of the University of Georgia to a $5 million, three-year contract.

When the ill-fated World Football League opened in 1973, NFL salaries increased by 19 percent annually, compared with 6 percent in the four seasons before the formation of the WFL.