The Scotsman will face second-seeded defending champion Sam Querrey of the United States in the first championship match at Los Angeles between the top seeds since Pete Sampras defeated Andre Agassi for the 1999 crown.
Querrey saved a match point in outlasting Serbian sixth seed Janko Tipsarevic 6-7 (3/7), 7-6 (7/5), 6-4.
Hometown favorite Querrey has won three titles on three different surfaces this season and could become the first back-to-back champion at the USD 700,000 hardcourt event since Andre Agassi defended his crown in 2002.
But Murray has a 4-0 lifetime record against Querrey, having won all nine sets they have played, including a straight-set triumph in the fourth round at Wimbledon.
"It was a tough match," Murray said. "He enjoys this court and he will receive good support so it's going to be another tough match."
Murray yesterday dominated the first set but struggled through the second, each loser being broken three times to force a third set. Murray broke to open the third set and held serve to the finish to claim the match.
"Throughout the match, right until the end, there wasn't one point where we both played very well," Murray said. "Neither of us played much since Wimbledon. Maybe that explains the inconsistency."
Murray joked that his ability to match Lopez's speed and quickness came from his mother's big calves, but added, "I've always had quite good anticipation."
Tipsarevic opened the third set with the first break of the match, denied Querrey on three break points in the second game after falling behind 0-40, then held to 2-0 on a net cord winner and a Querrey lob that landed wide.
Querrey broke back to 3-3 when Tipsarevic netted a forehand in the sixth game to surrender his first break of the match.
Tipsarevic squandered four break-point chances in the ninth game as Querrey held for a 5-4 lead and then the Serbian sent a backhand wide to give Querrey a break and match point in the 10th game.
Querrey netted a forehand but a double fault by Tipsarevic gave Querrey a second match point and this time he did not falter, taking the match after two hours and 47 minutes when the Serbian sent a backhand beyond the baseline.
"That was an awesome match, a lot of fun, a lot of drama," Querrey said. "When I got it back on serve, I felt I had the momentum. I got in a good rhythm."
Querrey squandered five set points in Tipsarevic's final service game of the first set, which went into a tie-breaker that the Serb dominated, bashing two service winners for a 6-1 lead.
After becoming upset over an umpire's call that one of his serves nicked the net, Querrey responded with a pair of forehand winners, but Tipsarevic then bashed a forehand winner to claim the opening set.
Tipsarevic had a match point with Querrey serving at 4-5 in the second set but three service winners in a row from the hometown favorite ended the threat and leveled the set.
The second set went to a tie-breaker as well and once again Tipsarevic jumped ahead, a pair of forehand winners giving him a 5-1 edge.
But this time, the American answered the challenge, swatting a forehand winner, two backhand winners and a service winner to level the tie-breaker.
Tipsarevic sent a backhand long to give Querrey a chance to claim the set and the Serbian then netted a backhand to send the match to a third set.
"I am happy by the way I played, but I should never lose this match," Tipsarevic said. "I didn't use the chances I had. I just missed too many easy balls trying to make a direct winner on them."
It was the third three-set escape of the week by Querrey, who needed a third-set tie-breaker to defeat Germany's fourth-seeded Rainer Schuettler in the quarter-finals.
"He managed to get out of two matches he should've lost," Tipsarevic said. "When it's important, he has coming up with big shots."