The Dutch crashed out of the tournament after their third straight loss in Group B when they went down 2-1 to Portugal on Sunday, Cristiano Ronaldo scoring twice after Rafael van der Vaart had grabbed the lead.
"I am responsible that we failed in this tournament, but I have a contract to 2016 [World Cup] and at the moment I am not thinking about my future," he told reporters at the Metalist Stadium.
"We started every match well, we started well tonight and the scenario was right at first, but then you have to keep that advantage and force your opponent to take more risks.
"But we didn't do that and then we gave away two goals too easily.
"I could see from my position with the equaliser, we made a mistake and were punished for it."
Heading into the game, the Netherlands only had a slight chance of advancing to the last eight after losing their opening two matches to Denmark and Germany.
Van Marwijk said it was always going to be difficult to progress after the awful start they had made to the competition.
"This was a special situation. If you play a final and draw it can go to penalties and you can win it that way, but we had to win by a two-goal difference - so we had to take risks and go forward.
"It started well, but then we didn't finish the job.
"Now is not the time to talk about my future right now. I am not thinking about it."
He also said he had tried to improve the team that lost to Spain in the World Cup final two years ago but acknowledged the balance may not be quite right.
"We have a lot of quality in the team. It's basically the same team as two years ago apart from one or two positions. We needed more pace and youth to make it better and have more strength in depth," he remarked.
"It's not an easy process and it was going to be difficult to repeat what we did two years ago, but although we started well today, mistakes let Portugal back into the game and that was the difference."
Van Marwijk also appeared to get the backing of the Dutch FA after the game when KNVB director Bert van Oostveen said: "I think this coach deserves some credit as he guided us to the World Cup final and also without any problems through two qualifying campaigns."
