Aug 12 (Reuters) - Defending champion Ben ⁠Shelton will face Brandon Nakashima for the Canadian Open title on ⁠Thursday after both Americans advanced in straight sets to the final ‌of a key U.S. Open warm-up event.

Fifth seed Shelton secured a 6-2 6-3 victory over Learner Tien under the lights in Montreal on Wednesday, snapping a two-match losing streak against ​his compatriot.

The big-serving left-hander was rarely troubled, though ⁠he required courtside medical assistance in ⁠the second set after crashing into the back wall and cutting his elbow ⁠and ‌left hand.

Shelton, 23, recovered quickly to close out the match and set up an all-American final with Nakashima, who earlier beat Spain's ⁠Rafael Jodar 7-6(3) 6-4 to reach his first Masters ​1000 final.

Nakashima, seeded ‌28th, found his range on serve early and took the opening-set tiebreak ⁠when Jodar ​sent a backhand volley long.

He had to work to seal the victory, needing five match points before firing down another booming serve that the Spanish teenager could only ⁠barely reach.

Nakashima, 25, has added greater variety to ​his game this season, a shift that helped him reach the semi-finals at Queen's Club and in Washington.

"Going into that last game I knew there was ⁠going to be some nerves," he told Tennis Channel.

"After the first few points it was obvious he wasn't going to be missing from the baseline so I knew I had to do something different and change it up."

Shelton ​has won all five of his meetings with Nakashima, ⁠their most recent encounter coming at last year's Canadian Open where he prevailed ​in three sets.

The last time there was an ‌all-American final at an ATP Masters 1000 ​event was in Cincinnati in 2003 when Andy Roddick beat Mardy Fish.

(Reporting by Rory Carroll; Editing by Tom Hogue and Peter Rutherford)