In a stunning announcement, Kansas City Royals outfielder Bo Jackson yesterday said that he planned to take up pro football as an offseason "hobby."

Jackson, in the second year of a three-year contract with the Royals, said that he intended to sign with the Los Angeles Raiders and would play for them as soon as his 1987 commitment to baseball ends, which could be as early as Oct. 5 or last late as Oct. 31.

In a brief press conference before yesterday's game in Toronto, Jackson twice emphasized that he would then return to baseball next spring, saying the Royals were his "No. 1 priority."

However, several sources near the Royals discounted such statements and said they believe that once he puts on the Raiders' uniform once, he'll never play baseball again.

And even if he intends to, he's going to face enormous problems. After yesterday's press conference, Jackson's teammates reacted with anger and skepticism.

"I think it's (bad)," Royals center fielder Willie Wilson said. "He is making us seem like we ain't crap."

As Wilson spoke near the batting cage at Toronto's Exhibition Stadium, several Kansas City players encouraged his critcism, yelling, "Speak for us! Tell it like it is!"

But Royals' co-owner Avron Fogelman, who attended the press conference with Jackson, said the Royals had agreed to the move because "the Royals think it is very important to do whatever is in Bo's best interests."

He added, "Bo is a member of the Royals, be assurred of that. The only way he will not be a member of the Royals is if we tear the shirt off his back. . . . He will be a Royal first, last and always."

However, sources said the Royals agreed to go along with the decision because they had no choice, that Jackson was ready to give up baseball altogether to play for the Raiders. Jackson's agent, Richard Woods, was believed to be in Los Angeles negotiating a contract with Raiders managing general partner Al Davis.

"Al believes if he ever once gets him in uniform, he's got him," an NFL source said.

However, Jackson insisted he hoped to play both sports.

"My No. 1 priority is the Kansas City Royals," he said. "Anything that comes after baseball is a hobby, like hunting or fishing. I may pick up another hobby after baseball. That's all it is, I'm thinking of adding another hobby."

Jackson then walked out of a news conference, saying, "I'm sorry but I've got to go to work now."

Many of his teammates thought he had quit the game Friday night when, after being removed for a pinch-hitter, he went into the visiting clubhouse at Toronto's Exhibition Stadium and cleaned out his locker.

Instead, he returned yesterday morning and appeared at a press conference in which Fogelman said the Royals would re-write the former Auburn running back's contract to remove a no-football restriction.

Jackson's decision to play baseball in the first place had been a controversial. After winning the 1985 Heisman Trophy, he was made the No. 1 pick in the NFL draft by the Tampa Bay Bucs, who offered him a five-year, $7.6-million package.

Instead, Jackson opted for a three-year, $1.066-million deal with the Royals, who took him in the fourth round of the baseball draft.

Since then, Jackson has insisted several times that he would never play football again. When the Raiders took him in the seventh round last April, Jackson hung a sign above his locker in Kansas City that said, "Don't be stupid-no football questions please."

But in recent weeks, he has begun to struggle and despite leading the Royals with 18 homers and 45 RBI, he has also struck out 112 times in 277 at-bats. His batting average, once above .300, has slipped in recently weeks, and was down to .253 after Friday's game.

"I would think this could be the end of baseball for him," said Charlie Casserly, the Washington Redskins assistant general manager. "What's his motivation to do this? There must be something in baseball that's bothering him. He might be with the Raiders now to stay."

Others wondered if it was physically possible to play both sports.

"Sure, he could do it," New York Giants General Manager George Young said. "But the question is, 'Can he play both sports well?' What do they say on those cigarette commercials, 'This is hazardous to your health.' I just don't know how it's realistic when the seasons overlap so much. Baseball is not a sport for the tender-hearted. You have to take out a guy at second base, run into fences and duck fastballs. Andre Dawson took one in the mouth the other day. It's illogical to me. Look at all the traveling they do, in and out of airplanes. Their routines are constantly interrupted. I wouldn't minimize the wear and tear on the body."

After stunning the Bucs by signing with the Royals last year, he played 53 games at Class AA Memphis last season before winning a late season promotion to the Royals. This spring, the Royals said they wanted to see him begin the season at Class AAA Omaha, but sources said Fogelman pressured his baseball staff to keep Jackson on the major league team.

"If he wants to play both, I wouldn't doubt him," Baltimore Orioles Coach and Hall of Famer Frank Robinson said. "With all he's already accomplished, you have to say it's possible."

Yet, his adjustment has been a tough one. He made base-running mistakes, threw to the wrong bases and left dozens of runners on base, which baseball people say is a product of rushing him to the big leagues. Where others confront those crises privately in places like Rochester and Omaha, he was doing it in New York and Chicago.

Meanwhile, his decision was met with skepticism and resentment in the Royals' clubhouse and among people connected with both sports.

"I got 900 restrictions in my contract of things I can't do because they're hazardous to my health," Wilson said. "How can you have Howie Long (defensive end for the Raiders) running into you for a hobby? You think Lawrence Taylor is going to think it's a hobby?

Jackson is signed with Kansas City through 1988 but his contract called for three escape periods, July 15 of each season, when he could return the Royals' money and play football. But his escape clauses stipulate he would have to return salary and bonus money if he abandoned baseball.

"Bo has not taken the route to walk out of his contract," Fogelman insisted.

Fogelman said Jackson will not be able to practice football on off-days so the most he will be able to play for the Raiders this season would be six to eight games.

"He wants to stay in shape, be active. He doesn't want to sit around all (off) season," Fogelman said. "He's looking for a hobby. He looks at it as a hobby. I think Bo can do both."