Conor Daly crashed at high speed into the Turn 11 tyre barriers.
Daly and Rasmussen banged wheels on Lap 12 of the Grand Prix of Portland and wound up touring the grass run-off.
Just a few minutes later, on Lap 15, they made contact at the high-speed chicane. Daly wound up worse off, spinning into tyres.
The Juncos Hollinger Racing driver walked away from the crash before speaking with host broadcaster Fox Sports.
“Honestly, I saw him drive Colton [Herta] almost into the wall on the back straight. That’s how I got Colton and got into position,” said Daly.
“[Rasmussen] was quite slow, so I tried to pass him into Turn 7, then again drove himself off the track to make sure I drove off the track, so I’m not really sure the point of that. It kind of seems stupid, in my opinion.
“Then he was really slow down the straight and I just went to pass him and then he just never stopped.
“That’s a really dangerous corner to be trying to do that. I feel like I had a lot more grip on reds (soft compound tyre) and I was pretty happy to turn in from there because I did it the lap before on Colton, but he just never stopped. I would say that was quite an unsavoury move.”
Taking to social media, Daly went in even harder on Rasmussen.
“Purposefully wrecking someone in a 150mph corner is just pure insanity,” he wrote.
“That’s not racing. It’s inexcusable. The driving standards, for some, are a joke right now. That means you, Christian Rasmussen.”
Rasmussen admitted the first incident at Turn 7 was hit fault after suffering understeer, which led to awkward contact with the floor of Daly’s car and ripped the steering wheel out of the Danish driver’s hands.
Nevertheless, the Ed Carpenter Racing driver wouldn’t take any blame for the clash at Turn 10 – a view he believed was right, given he went unpenalised by officials.
“Well, I think that’s what you can expect to happen if you try to roll the outside in Turn 10, which is obviously the quickest corner on the track together with me being alongside him,” he explained.
“I don’t know if he just expected me to pull out of it, but I was pretty much like this (gesturing side-by-side) on him.
“I’m on the inside, so I wasn’t going to hold out. Obviously the race control saw it the same way. I don’t know. Not much more to add to it.
“Seven, I agree that was on me. I picked up understeer and my wheel touched his floor in a weird way, which knocked the wheel out of my hand, he added.
“That’s on me, that’s my fault. Turn 10, I think that’s what you can expect when you can try to roll the outside in a corner like that.”
Daly was classified 26th while Rasmussen went on to finish 12th.
IndyCar continues on August 25 (AEST) at the Milwaukee Mile. The season concludes at Nashville Superspeedway on September 1 (AEST).