Mitch Kupchak made two free throws and drew a key charging foul, all in the final 18 seconds yesterday, to lead the Washington Bullets to a 93-90 victory over the Houston Rockets and a 2-1 lead in their best-of-seven National Basketball Association Eastern Confernece semifinal playoff series.

Kupchak, who led the Bullets with 23 points, was fouled by Moses Malone as he went up for a dunk after taking a pass from Phil Chenier with 18 seconds left. His two free throws gave the Bullets a 91-90 lead.

At the other end of the floor, Kupchak stepped in front of Mike Newlin as the Rocket guard drove for the basket after getting past Chenier. Newline was called for a charge with 11 seconds left and the Rockets were done.

The Rockets were forced to foul and Rudy Tomjanovich grabbed Chenier with seven seconds left. Chenier made two free throws to account for the final margin.

It was a physical game throughout and not very many people were backing down.

Elvin Hayes converted a three point play over Dwight Jones with 3:05 to play to break the Bullets away from and 86-86 tie, but Washington didn't make another field goal.

After a series of missed layups and turnovers by both teams, Malone put the Rockets within a point on a pair of free throws after being fouled by chenier.

Hayes was called for walking on the Bullet's next possession and then, with 58 seconds remaining, Malone picked up a loose ball under his basket and in one motion, threw in a one handed turnaround slam dunk from eye level with the rim. That gave the Rockets a 90-98 lead.

Hayes then missed a layup with Malone rebounding for Houston. The Rockets called a time-out with 34 seconds to play.

John Lucas drove to the basket and then pulled up for a 15-footer, but the Bullets' Tom Henderson was waiting for him and swatted the ball to Wes Unseld and the Bullets called time-out with 28 seconds to play.

Washington called a play designed to get Chenier a shot. Unseld inbounded the ball to Chenier who drove to his right and then back toward the middle. As he got the basket, Jones swithced off Kupchak to help out. Chenier dumped the ball to the open Kunpchak.

Malone rejected his dunk attempt, but hit Kupchak with his body, sending the Bullet to the foul line with 18 seconds left.

The Rockets screamed in anger at the call while the Capital Center crowd of 16,842 went wild.

Kupchak calmly made both free throws and the Bullets had a one point lead.

The Rockets called time-out to get the ball at midcourt.

"We figured they'd go to Newlin on a drive, or kick it down to Malone," Bullet coack Dick Motta said.

The Rockets chose Newlin, who had made seven of eight shots from the field Newline faked Chenier after getting the inbounds pass from Tomjanovich and drove toward the basket.

Kupchak saw Newlin getting free and stepped into his driving lane. The foul call went Kupchak's way.

"It was close," Kupchak said. "It could have gone either way. I was moving just a little bit, but Newlin had made up his mind to go all the way."

Newlin said he saw Kupchak and "jumped to the side. I didn't jump into him, but I'm not the referee."

The Bullets started out yesterday as if they were going to make short work of the RocketS.

Kevin Grevey scored Washington's first seven points and the Bullet's raced to a quick 22-8 lead.

The Rockets called time-out and Lucas came back as if he would single-handledly lead them back.

Houston ran off 12 straight points, eight of them by Lucas, six of them off fast breaks and the visitors were back in business.

Another Lucas binge at the end of the half brought the Rockets to a 50-47 halftime lead. He scored driving eight possessions of the half and assisted on a NewLin fast break. The Bullets, meanwhile, turned the ball over four times, missed three shots and got one basket - from Grevey - on their last eight possessions.

Lucas scored on a drive to his right to cut the Bullet's bail away on Grevey's dribble to Jones, who fed Lucas for an easy basket and a one-point Rocket deficit.

Grevey missed at the Bullet's end and Lucas rebounded it and then threw a long pass to the streaking Newlin and the Rockets were on top 48-47.

Lucas had 16 points in the first half, but only two after that. Henderson was the reason.

Lucas likes to drive to his right and pull up for a short fadeway, lefthanded shot that is hard to block.

"The second half I came out pushing him," Henderson said. "I think he was starting to get a little frustrated after a while, but he was cool. A couple of times he even said, 'Good defense, Tommy.'"

Between them, Hays and Chenier made only 12 of 35 shots, but the Bullets seemed to come up withthe big baskets when they needed them.

"We just didn't pick up the tempo," Henderson said. "Anytime we don't score 100 points, it's not our type of game."

The fourth game of the series will be played Tuesday at Capital Centre, with the remaining games alternating between the Summit in Houston and Capital Centre.