LeT which "has claimed responsibility for the 2008 Mumbai terrorist attacks that killed at least 163 people," was also "responsible for the May 23 attack on the Indian Consulate in Herat, Afghanistan," the State Department said Wednesday.
The attack three days before the swearing in of the new Bharatiya Janata Party (BJP) government was apparently aimed at derailing Prime Minister Narendra Modi's initiative to reach out to India's South Asian neighbours.
"The designations help us cut off support and funding to LET so they can't undertake future attacks," State Department spokesperson Mary Harf told reporters Wednesday.
"Cooperation between the United States and India has already led to several Mumbai terrorists, including David Headley, being brought to justice," she said.
Born Daood Sayed Gilani to a Pakistani father and an American mother, the key plotter of the Mumbai attacks had changed his name to David Coleman Headley at the instance of LeT to avoid attention as he scouted targets for the attack.
"To date, the Department of Justice and FBI have provided extensive assistance to the Government of India in their investigations into the Mumbai attacks, including access to interview David Headley and substantial additional evidentiary evidence as well," Harf said.
President Barack Obama "and everyone have been very clear that we will continue working to bring other perpetrators of this attack to justice," she said.
Asked if the US was considering giving India another round of access to David Headley and his co-accused Tahawwur Hussain Rana, the spokesperson said the justice department and the FBI "would probably be better able to speak to that."
The terrorist designations of LeT have been amended to add Jama'at-ud-Dawa, headed by the mastermind of Mumbai attacks Hafiz Muhammad Saeed, Al-Anfal Trust, Tehrik-e-Hurmat-e-Rasool, and Tehrik-e-Tahafuz Qibla Awwal to its list of foreign terrorist organisations.
At the same time targetting LeT's financial and leadership networks, the Treasury department also designated two senior LeT members - Nazir Ahmad Chaudhry (Ahmad) and Muhammad Hussein Gill- as Specially Designated Global Terrorists (SDGTs).
The new sanctions include a prohibition against knowingly providing material support to these organizations, and the freezing of all property and interests in property of the organizations in the US.
"In targeting Lashkar-e-Taeba leadership, today's action demonstrates our unrelenting commitment to combating terrorism by disrupting terrorist groups' financial activities," said Under Secretary for Terrorism and Financial Intelligence David S. Cohen.
"We will continue to target LeT's financial foundation to disrupt and impede its violent activities," he said.
After the 2008 Mumbai attacks, LeT was responsible for multiple terrorist attacks, mostly in Jammu and Kashmir in 2011, State Department said.
In 2012, LeT claimed responsibility for an attack against an Indian army convoy in Kashmir that killed one civilian and injured two others.