Nikola Jokic led a second-half fightback as the Denver Nuggets completed a 4-0 Western Conference championship sweep over the Los Angeles Lakers on Monday to reach the NBA Finals for the first time in franchise history.

Two-time NBA Most Valuable Player Jokic finished with 30 points after the Nuggets overturned a 15-point half-time deficit to send LeBron James and the Lakers crashing out of the postseason with a 113-111 victory at the Crypto.com Arena.

James had looked to be single-handedly keeping the Lakers' season alive after scoring 31 points in a magnificent first-half display that left the 17-time NBA champions leading 73-58 at half-time.

But Jokic led a resurgent Nuggets offense in the third quarter, scoring 13 points as the Western Conference top seeds outscored the Lakers 36-16 to turn the contest on its head.

A dramatic fourth-quarter finale saw Jokic put Denver 113-111 ahead with a typically barnstorming driving layup through heavy traffic with 51.7sec remaining.

With four seconds remaining James had one last chance to tie it up and force overtime, but his attempted driving floater was blocked by Denver's Aaron Gordon to leave the Nuggets celebrating a famous win.

Denver — one of 11 teams in the league who have never won the NBA championship — will face either the Miami Heat or Boston Celtics in the finals.

Miami, leading Boston 3-0, can clinch their place in the finals with a victory at home on Tuesday.

"We don't give up," Jokic told ESPN. "I've been saying this for five years — when we were bad or when we were good — we don't give up. And that's what happened today.

"They jumped on us the first half, they were better, more aggressive, scoring easily and didn't miss basically.

"But in the second half we turned the page and everybody stepped up. It was a collective effort, it's not just one guy."

The Nuggets will head into the finals brimming with confidence that they can end their near-half-century wait for a maiden NBA crown after another composed all-round performance proved too much for the Lakers.

The 38-year-old James finished with 40 points, 10 rebounds and nine assists for the Lakers in a heroic attempt to keep the series alive.

"He had an amazing game," Jokic said of James. "We couldn't stop him in the first half… he's still one of the best to ever play this game."

But the Lakers' supporting cast once again failed to step up when it mattered, with a series of missed baskets in the fourth quarter allowing the Nuggets to hold on to their slender advantage to clinch victory.

Lakers head coach Darvin Ham said his team had paid the price for not making enough shots, praising Denver's ruthlessness down the stretch.

"The sign of a great team is if you make any mistake, they're going to make you pay for it," Ham said. "And they did just that."

Ham, who was appointed last year with a brief to rebuild the Lakers after a dismal failure to reach the playoffs, insisted that the NBA giants were on the right path.

"This is year one," Ham said. "Losing sucks, but I think we can do something special here."