The victory marked the 15th consecutive win for Team USA in WBSC U-18 World Cup action, including the final seven contests of the 2015 version of the event, held in Osaka, Japan.
The three-time defending World Cup champions, the U.S. remains the only undefeated team in this year's tournament with an 8-0 record and will play as the home team in Sunday's gold-medal game at 5 p.m. ET. Team USA's opponent will be determined later on Saturday afternoon following games between Japan-Korea and Canada-Cuba.
Dieter faced just three batters over the minimum, did not allow a baserunner past first base, and struck out eight over eight innings of three-hit ball to earn the win. Joseph Menefee (Richmond, Texas) then pitched a 1-2-3 ninth to close out the contest.
Saturday's game marked the second in this year's World Cup in which the U.S. pitching staff did not allow a runner past first and the fourth in which a runner did not advance past second.
The red, white, and blue will carry a combined 0.53 ERA into Sunday's gold-medal game with opposing batters hitting just .136. Team USA's five shutouts equal the total for the other 11 teams in the tournament combined.
Offensively, the U.S. was terrific with two outs once again, recording seven two-out hits and scoring all but two of its runs with two outs on the scoreboard.
Five different players notched multi-hit contests, while Alek Thomas (Chicago, Ill.) and Nolan Gorman (Glendale, Ariz.) drove in a pair of runs each. Team USA also added five stolen bases against Australia, including two from Gorman, to increase its tournament-leading total to 23 in just eight games.
The U.S. wasted little time getting started on Saturday with Mike Siani (Glenside, Pa.) and Carter Young (Selah, Wash.) opening the home half of the first with back-to-back doubles for the game's first run.
Thomas and Gorman's big knocks both came in the third which ended up being a five-run inning to break the game open for Team USA. A Will Banfield (Lawrenceville, Ga.) run-scoring single in the fifth and RBIs by Jarred Kelenic (Waukesha, Wis.) and Triston Casas (Pembroke Pines, Fla.) in the eighth accounted for the game's final tally.
Team USA is the three-time defending World Cup champion and is looking to become the second country to win four consecutive gold medals in the tournament.
Continue to follow @USABaseball18U on Twitter and visit USABaseball.com for the most up-to-date news about the 18U National Team.
USA Baseball 18U National Team Manager Andy Stankiewicz
(On Saturday's win over Australia)
"It all started with Brandon Dieter. He's just a machine. He commands his fastball so well in-and-out, has a beautiful changeup, and a nice breaking ball. He took control of the game from the get-go. He let up that leadoff hit then he picked the guy off and that set the tone and got the momentum back on our side. A great job by him, first and foremost. Our mission is to win every game we play. We are encouraged by what we have done so far, but we all know the big one is tomorrow. Hopefully this was a nice tune-up, the guys feel good about their at-bats, and we can take that into tomorrow."
(On available pitching for the gold-medal game)
"We feel like we are in a good spot going in to the gold-medal game. We have a lot of arms down there and it will be all hands on deck. They have to be ready to roll. It was a big game by (Brandon) Dieter, obviously, and I loved the job that (Joseph) Menefee did. He came in and got strike one right away. He'll be ready to go tomorrow, if needed, too."
(On the team's two-out offense)
"The guys are understanding that just because we have two outs the inning isn't over. If we get that next guy on, our ability to run and hit in motion allows us really put pressure on the defense. Coach Mosiello has done a great job of keeping our guys in motion and creating that pressure. That is the way we have to do it. We can't give away any at-bats."
(On the team's mindset going in to tomorrow)
"We just need to play our game. Sometimes in big moments like we will have tomorrow guys try to be something they are not. We just need to be who we are, understand our roles, and come out tomorrow as a team and get after it."
Starting Pitcher Brandon Dieter
(On his goal on the mound today)
"My number one goal today was to be efficient. The coaches wanted me to go as many innings as I could so being efficient was the key. Throwing a lot of strikes, getting ahead early, and getting a lot of first-pitch outs was huge today."
(On playing for the gold medal tomorrow)
"This is what we came here to do, to win this game tomorrow. To be able to give some rest to the rest of our pitchers and allow everyone to be on deck tomorrow was my goal today. I achieved that and it is all hands on deck tomorrow because we are going out to win a gold medal."
(On the 18U national team playing for a fourth consecutive gold medal)
"We all know it, it is in the back of our heads. We want to keep that streak going, no one wants to break that streak. But, like the coaches have been saying, we have been playing one pitch at a time, one game at a time, and taking it step-by-step. I think that is what is making us successful so far."
Infielder Nolan Gorman
(On having two hits versus Australia)
"I was just trying to anything I could for the team by putting the ball in play, which I haven't been doing. It's starting to come around though and it felt good to barrel up a couple of balls."
(On the team's offensive mindset)
"We are seeing it really well right now which is good going into the gold-medal game. If we can just carry that into tomorrow, we should be alright. The goal has always been to win every game and not let down against anybody. We are happy to get this win today but we have one more before we can celebrate anything."
(On the experience of playing for Team USA)
"It is special. There really aren't any words for it yet. Maybe after I get home and have some time to let it sink it, but there are no words to describe it right now. It is just so special."