Tankian, whose grandfather is a survivor of the atrocities, demonstrated outside the office of US House of Representatives speaker DENNIS HASTERT, along with several members of the Armenian National Committee (ANC), in a bid to get official condemnation of the slaughter of his countrymen at the hands of the Turks between 1915 and 1917.
He says, "We're trying to encourage him to do the right thing historically, morally and even politically.
"Europe, South America, Canada and 38 out of 50 states in the US have already recognised what happened as genocide, so it's a historical fact.
"If the US as a nation recognised the genocide, because it is such a close ally of Turkey, it would help Turkey deal with its own past.
In a letter to Hastert, Tankian wrote: "My grandfather STEPAN HAYTAYAN is a 97-year-old survivor of the genocide. He's my only link to the past. I promised him I would try to reach you and explain how important American recognition is to the surviving children of the first genocide of the 20th century."