Balwinder Singh, an Indian citizen holding a Green Card, made the admission before Federal Judge Larry R. Hicks in Reno, Nevada state, on Tuesday that he provided a co-conspirator with night vision goggles for the planned attack as a part of their terrorist conspiracy.
Singh's conspiracy "was part of a movement to create an independent Sikh state in Punjab", according to a statement by the prosecutors.
"Singh attempted to provide material support and resources to terrorists to create violence and disruption abroad," said acting Assistant Attorney General Mary McCord.
"Identifying, thwarting and holding accountable individuals who pursue international terrorism is a top priority of the Department of Justice," she said.
Prosecutors said the conspirators were to decide on the government official to be targeted after one of them reached India.
Singh's co-conspirators in the plot uncovered by US officials in 2013 were not identified.
But prosecutors said the law enforcement officials caught one of them in San Francisco on December 9, 2013 while trying to board a flight to Bangkok on way to India to carry the terror attack.
"As a result, the planned attack never occurred," the statement said.
That person was carrying the night vision goggles provided by Singh.
Singh and the co-conspirators, however, continued to plan terror attacks to be carried out in India till he was arrested on December 17, 2013, according to prosecutors.
Singh, 42, who goes by the aliases Jhaji, Happy, Possi and Baljit Singh, has been in jail since his arrest and could face a maximum sentence of 15 years in prison when he is sentenced in February.
"Today's (Tuesday) plea is the result of the FBI's Joint Terrorism Task Force working pro-actively to disrupt terrorist attacks," said Daniel Bogden, the federal prosecutor in Nevada.
"We will continue to work with our law enforcement partners to locate, identify, and prosecute those who conspire and attempt to provide material support to terrorists and terrorist activities."