Polanski lost an appeal to be released on bail earlier this week
Swiss authorities have said they acted correctly in telling the US that Roman Polanski was travelling to Zurich.
It was this tip-off that set in motion the 76-year-old director's arrest last month for pleading guilty to unlawful sex with an under-age girl in 1977.
Swiss Justice Ministry spokesman Folco Galli said: "An arrest is a big operation and we needed to know if the warrant was still valid."
After receiving confirmation, he said that Switzerland was obliged to act.
"The Americans immediately confirmed that was the case," Mr Galli said.
Imogen Foulkes, BBC News, Bern
The Swiss authorities say they were simply following normal procedure in letting the US know Roman Polanski was due in Zurich, but questions remain.
Mr Polanski has been a regular visitor to Switzerland for many years and owns a holiday chalet in the resort of Gstaad. But his official presence at the Zurich Film Festival - where he was due to be welcomed by the head of Switzerland's office for culture - may have been seen as too public an event for the Swiss authorities to permit.
Polanski was taken into custody in Zurich after he travelled from France to collect an award at the city's film festival.
He has been wanted in the US since pleading guilty to unlawful sex with an under-age girl and then fleeing in 1978.
Galli also addressed the question of why Switzerland had decided to detain Polanski now, despite the director travelling to and from the country - where he owns a house - several times in the last 30 years.
He said this was the first time officials had had precise details on the director's travel plans at the same time as an official American request to arrest him.
Galli's comments follow the emergence of documents - revealed by AP following a public records request - which shed light on how the US came to be aware of the fugitive director's movements.
1977 - Polanski admits unlawful sex with Samantha Geimer, 13, in Los Angeles
1978 - He flees to Britain after US arrest warrant is issued. He immediately moves to France, where he holds citizenship. He settles there - protected by France's limited extradition with US
2008 - Polanski's lawyer demands case be dismissed and hearing moved out of LA court
2009 - Polanski's request to have hearing outside LA is denied. Swiss authorities detain Polanski after he travels to Zurich
After receiving the tip-off, US federal officials alerted prosecutors in Los Angeles who drafted an arrest warrant.
The US authorities had declined to say how they learned of Polanski's trip to Zurich.
Laura Sweeney, a spokeswoman with the US Department of Justice, said: "We don't comment on matters of extradition unless and until an individual is on US soil."
Earlier this week, Polanski lost an appeal to be released on bail from the Swiss jail where he is being held ahead of his possible extradition to the US.
Switzerland's highest criminal court backed an earlier government ruling that there was a high risk of him fleeing the country if he was released.
Polanski plans to appeal against the decision, but his lawyer told France's Europe 1 Radio that his client could conceivably end up in the US.
"We could be heading towards an extradition if the Swiss justice system does not take into account arguments against it," Georges Kiejman said.
"If the procedure drags on, it is not impossible that Roman Polanski could choose to go and explain himself in the United States, where there are some arguments in his favour," he added.
However, fellow lawyer Herve Temime - also based in Paris - denied that the director's legal team was now considering waiving extradition.
"We continue to fight extradition, and for him to be free," Temime told The Associated Press. "There is absolutely no change of strategy."
The Paris-born Polish filmmaker has not set foot in the US for more than 30 years.