"Foreign terrorist organisations like LeT use internet propaganda to radicalise and recruit individuals to wage violent jihad and spread terror," Neil H MacBride, US Attorney for the Eastern District of Virginia, told reporters here.
LeT is responsible for a number of terror attacks such as the 2008 Mumbai strikes which killed 166 individuals, including six Americans -- two of them from Virginia.
Referring to the conviction of Pakistani national Jubair Ahmad, a resident of Virginia, for supporting LeT, MacBride said the US would pursue all those who provide material support to terrorists.
This is the fifth case of home-grown terrorism in eastern district of Virginia that FBI has brought in the last year.
"It's a significant threat that we take very seriously," MacBride said.
Describing LeT as a "dangerous and deadly" foreign terrorist organisation, he said: "Over the years they have tried to change their name. And each time the US government has responded by classifying their pseudo or nick names as the foreign terrorist organisations."
Ahmad, 24, pleaded guilty before a US court of charges that he provided material support to LeT.
"This demonstrates our tireless commitment to disrupt and dismantle (what) we consider to be material support (to the terror outfits). We take radicalisation on the internet, on any firms of recruitment extremely seriously," said Brenda L Heck, Special Agent in Charge for FBI's Washington Field Office Counter-terrorism Division.
Ahmad told the court that he prepared and uploaded a 'jihadi' video on You Tube at the direction of Talha Saeed, son of the LeT commander Hafiz Saeed.
Court documents allege that during his teenage years in Pakistan, Ahmad received indoctrination training from LeT and later immigrated to the United States with his family in 2007.
In September 2010, Ahmad allegedly conspired with Talha to produce a propaganda video for LeT, which contained images showing violent 'mujahideen' operations while a prayer by the LeT leader is heard in the background, calling for the support of 'jihad' and the 'mujahideen'.
"LeT is a ... deadly organisation. The head of the organisation is an individual whose voice appears on the video tape. It's a lecture or prayer that calls for violent jihad. The son of that individual (Talha) contacted him (Ahmed) to prepare that video.
"So he (Talha) is a significant person within LeT and has the ability to reach out to someone here in Northern Virginia," MacBride told reporters in response to a question.
Although the name Mumbai pops up during the investigation of this case, MacBride said there is no information on the Mumbai terrorist attacks from this probe.
According to the plea document, at one point, Ahmad asked Talha if he wanted to include an image of the Mumbai attacks to show the power of LeT. Talha replied that he should not use anything referring to Mumbai.
"The significance is that this man, Mr Ahmad probably volunteered to make a video tape to recruit and radicalise new jihadists to join LeT," the US attorney said.