Brian Gottfried made the most of one of those rare days when Harold Solomon couldn't quite recharge his batteries and yesterday moved into the final of the $125,000 Washington Star International tennis championships.

Gottfried will meet top-seeded Guillermo Vilas of Argentina in the final. Vilas defeated fifth-seeded Eddie Dibbs in the evening semifinal, 7-6. (7-5). 6-2.

Tonight's final will be Gottfried's ninth in 16 tournaments this year.

Gottfried, who had won only two of eight previous career meetings with Solomon on clay courts, decided after some unsuccessful first-set experimentation to play his own aggressive game. He beat the 1974 champion from Silver Spring, 4-6, 6-3, 6-1, to the surprise of most of the 5,600 at Washington Tennis Stadium.

Gottfried, who won the Volvo Classic at George Washington University in March, will go for the $20,000 first prize tonight at 7:30 against the winner of last evening's semifinal between No. 1 seed Guillermo Vilas, who lost to Solomon in the 1974 final and beat him for the title in 1975, and Eddie Dibbs.

The Public Broadcasting Service will televise the final nationally, and WETA-TV-26 will carry it locally by "tape delay" starting at 10 p.m.

Although Gottfried, the No. 2 seed, has won four tournaments this year, was runner-up in the French Open, leads the Colgate Grand Prix standings and is No. 3 in the computerized world rankings of the Association of Tennis Professionals most people expected Solomon, the lion-hearted clay-court scrapper, to win.

But Gottfried played an intelligent match, lobbed exceptionally well in the tricky wind that rustled the green and white-striped canopies at 16th and Kennedy Streets NW, and capitalized on the opportunities Solomon gave him by hitting too short too often and making far too many unforced errors.

"I wasn't getting enough depth on the ball and I seemed to be giving him at least one easy point, a careless error, every game. That got me in trouble all the time," said Solomon, the No. 6 seed, after the 1-hour, 53-minuted match.

Solomon couldn't summon his usually deep reserves of energy when he got behind. He did come back to 3-4 after being within one point of a 1-5 deficit in the second set, but then immediately played a bag game to lose his serve at 15.

He lost his serve again after leading 30-0 in the first game of the final set, which is thought was the most crucial game, and was down 0-4 before getting himself psyched up for one of his celebrated last hurrahs. It was too little, too late.

"I really didn't get fired up until 1-4. I had a break point in that game before I lost it. I thought I still had a chance there," said Solomon, who at 24 is a year younger than Gottfried.

"I finally got a little adremalin going, a little inspiration. I thought if I broke him for 4-2 I could get back into it . . . But it wasn't quite there."

Solomon had won 13 consecutive matches in the last 2 1/2 weeks, three in the round-robin WCT Tournament of Champions at Lakeway, Tex., six in route to the Western Open title at Cincinnati last week, and four in reaching the quarterfinals here.

It was the last two matches that undoubtedly took the greatest toll. Solomon collapsed with cramps within seconds of beating Phil Dent, 6-7, 6-4, 7-6, in a physically and emotionally exhausting struggle Friday night, and he again came back after losing the first set of a tough match against John Alexander Saturday evening.

"I think he got a little mentally tired, and I was able to stick in there and hit the good shots when I needed them," said Gottfried. "I felt great. I never felt the least bit tired, which is unusual when you play Solly. I'm sure those last two matches took something out of him."

Solomon had won his last three meetings with Gottfried, held a 10-6 career advantage, and had not lost to him on clay since the fall of 1975, when Gottfried won in straight sets at Melbourne, Australia.

Solomon won the first set, but did not feel he controlled it. "I never felt the ball really well," he said, "He was hitting pretty hard, and I was a little slow, a half-step behind where I should have been to get in position for my shots. Consequently, I was hitting short all the time."

Gottfried was trying to hit short in the first set, bringing Solomon to the net to test his less-than-formidable volley. But that is not Gottfried's natural game, and he was no doing it well.

He decided to change his tactis early in the second set, going to the net behing more of the serves he was spinning in at three-quarters pace, looking to attack the short ball and get to the net behind very reasonable approach shop. In short, he decided to play his own style and see if Solomon's passing shots were up to defusing it. They were not.

Gottfried held his serve for 2-1 with three aces, the last on a second serve, then broke Solomon at love and held again at love for a total of 12 straingt points.

Solomon held serve from 30-40 before breaking Gottfried after one deuce with a beautiful forehand down-the-line winner. But he then played a terrible game to lose his serve for 3-5. He double faulted to 15-30, Gottfried got in for a forehand cross-court volley winner, and Solomon made one of his numerous unforced forehand errors for the break.

Gottfried, confident now, served out the set and broke to start the third set. From 30-0, he passed Solomon with a forehand off a ball that skipped off the net cord. Then Solomon double faulted and netted a backhand to 30-40, and, after saving a break point, hit a forehand cross-court wide on the second.

"That was a bad game to lose.After that, he just played too well. he kept the pressure on the hit the ball better than I did," said Solomon. "I didn't have much left after that."