Huckabee Sanders said Saeed's release "sends a deeply troubling message about Pakistan's commitment to combating worldwide terrorism and belies Pakistani claims that it will not provide sanctuary for terrorists on its soil", adding that, "If Pakistan does not take action to lawfully detain Saeed and charge him for his crimes, its inaction will have repercussions for bilateral relations and for Pakistan's global reputation".
He was under house arrest since January this year but freed by Pakistan this week.
Mr Saeed, 68, has always denied being being the multi-target attack on Mumbai that left close to 170 people dead.
Saeed's release could once again sour US relations with nuclear-armed Islamabad, which had seen an apparent improvement after the rescue by Pakistan's military of American hostage Caitlan Coleman and her family on October 13.
Indian and U.S. authorities were also outraged at Friday's release of Saeed.
It also called Saeed a "notorious terrorist" and pointed out that "a clear worldwide consensus" exists regarding Saeed's culpability - he was designated by the United Nations under UN Security Council Resolution 1267 in December 2008 and the Department of the Treasury has designated him a Specially Designated Global Terrorist.
In a statement, US State department spokesperson Heather Nauert said, "The United States is deeply concerned that Lashkar-e-Tayyiba (LeT) leader Hafiz Seed has been released from house arrest in Pakistan".
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A Pakistani court released Hafiz Saeed, who heads the banned charity group Jamaat-ud-Dawa (JuD), from house custody on Wednesday.
The US, since 2012, had announced $ 10 million for information that brings Saeed to justice. "They play everyone, whether it's China or the terrorists or us".
"Ousted Prime Minister Nawaz Sharif has been punished for neglecting Kashmiris".
The United States today engages in extensive economic, social, and scientific assistance as well as vital military relations with Pakistan, which is believed to own a stockpile of 80 to 100 nuclear weapons.
Saeed attacked government of Pakistan for "taking dictation from foreign masters" and spoke about "Indian atrocities" in Kashmir. Police guards have been removed from his residence where a large number of supporters gathered to celebrate the end of his house arrest.
Earlier, India had slammed Pakistan for its decision to release Mumbai attack mastermind who was under house arrest for ten months.
India-Pakistan relations are already at a low ebb, particularly under the ruling Hindu-nationalist Bharatiya Janata Party, but Saeed's release will reinforce the view from New Delhi that peace talks would be pointless while the military is allegedly overpowering civilian institutions, Pant said.