US Ambassador on Friday said release of Zaki-ur-Rehman Lakhvi, the 26/11 Mumbai terror attack mastermind, from jail, was "a mistake" and his country has already shared its concern on issue with Pakistan.

"We have shared our concern about this issue. We have raised it with the Pakistani government and we have been very clear that the perpetrators of those in the attacks of Mumbai have to be brought to justice," Verma said in an interview with news channel CNN-IBN.

"The release of Lakhvi is a mistake," he said.

On being asked that what action can the US take on the issue, specially when it has sold a billion dollars worth of weapons to Pakistan, he said terrorism of Pakistan faces is a challenge to all and so the aid that goes to Pakistan is to support democratic reforms and civic society.

"It also provides them the tools to combat this dangerous insurgency. But we also have to communicate our differences when we have them crack down on safe havens. The president (Barack Obama) has been very impelling on that and to crack down on the perpetrators and to hold them accountable will continue to erase them," Verma said.

Lakhvi, who is among seven people charged with planning and helping to carry out the 2008 Mumbai terror attack, was released from a jail in Rawalpindi in April this year, after the Lahore High Court suspended his detention and ordered his immediate release.