(CNN) - If the Malaysia airliner in Ukraine was shot down, then the United States will need to take action against the assailants, two Republican senators argued Thursday.
"If it is the case, then we're going to have to act and act in the most stringent fashions, including real sanctions, including giving the Ukrainians the ability to defend themselves, which we have not done so far," Sen. John McCain, R-Arizona, said in an interview with CNN's Anderson Cooper.
While early speculation about the crash has focused on the possibility of the plane being shot down, it's still unclear exactly what caused the tragedy.
McCain emphasized that he doesn't know how the plane crashed, but also argued that if the incident was caused by pro-Russian separatists, as Ukrainian officials have claimed, then the violent situation on the Ukrainian-Russian border could require heightened intervention by the U.S.
"If, if - I keep emphasizing if - it was a missile that was launched, either by Russia, or the quote separatists which in my view are indivisible, it would have the most profound repercussions," said McCain, who serves as the ranking member of the Senate Armed Services Committee.
"It would open the gates for us assisting, finally, giving the Ukrainians some defensive weapons (and) sanctions that would be imposed as a result of that. That would be the beginning."
Sen. Lindsey Graham, R-South Carolina, told CNN's Lisa Desjardins that if the plane was shot down by Russians or pro-Russian separatists, it would be a "game changer."
“If they are responsible – and I have no idea they are – you would take the sanctions we’ve unilaterally imposed, toughen them and get the world behind them," he said. "Start arming the Ukrainian military is what I would do.”
Graham also sits on the Senate Armed Services Committee.
Meanwhile, McCain argued there would be no strategic reason for either side to intentionally bring down a passenger jet, saying it must have been a mistake, if in fact it was hit by fire.
"It's impossible for me to imagine this thing being - if it is a shoot down - nothing but a tragic mistake on their part," he said.
“I just cannot believe that no one in their right mind would want to shoot down an airliner.”