BERLIN - A senior ally of German Chancellor Angela Merkel says he's open to launching a parliamentary inquiry into whether authorities made mistakes in handling the Tunisian man who drove a truck into a Christmas market in Berlin.

Attacker Anis Amri had been rejected for asylum in Germany but authorities had been unable to deport him. Amri, who had used at least 14 different identities since coming to Germany, also was on their radar as a potential security risk.

Volker Kauder, the caucus leader of Merkel's conservative Union bloc, noted Saturday there are questions whether there were coordination problems between federal and state authorities, news agency dpa reported.

He added: "If one of is of the opinion that more needs to be done here, I am open to a committee of inquiry."