United States, the largest market for the $282 billion Indian IT sector, is a "wild card" for the industry, lobby grouping Nasssom's president Rajesh Nambiar said on Monday.Speaking to reporters Nambiar said the tariff threats by the US may turn out to be the biggest headwind for the sector."Broadly, if you were to look at the headwinds, the biggest unknown there would be the tariffs and the impact of what happens in the US market," Nambiar said.