Senator John McCain (R-Arizona) declared on Thursday there would be "incredible repercussions" if Russian forces or pro-Russian separatists in Ukraine shot down the Malaysian flight that crashed earlier in the day.

In an appearance on MSNBC shortly after news of the crash broke, McCain stressed it was too early to come to definite conclusions. However, he pointed out Ukrainian aircraft have previously been shot down in recent days and "mistaken identification" of the Malaysian plane could be "part of a pattern" that demands a powerful reaction from the United States.

"This was an airliner headed towards Russian airspace and it has the earmarks — and I'm not concluding — but it has the earmarks of a mistaken identification of an aircraft that they may have believed was Ukrainian. If that's true, this is a horrible tragic event which was certainly unanticipated by anybody no matter who they are. And there will be incredible repercussions if this is the case," he said. "If it is the result of either separatist or Russian actions mistakenly believing that this is a Ukrainian warplane, I think there's going to be hell to pay and there should be."

McCain called the pro-Russian separatists and the Russian government "really one and the same" and said both had the capability to shoot down the Malaysian flight. An adviser to the Ukraine interior minister said separatists shot down the passenger plane with a Russian-made Buk ground-to-air missile system. The separatists have denied responsibility. Ukrainian forces have been clashing with the separatists in the eastern part of the country and the region of Crimea since pro-Kremlin Ukrainian President Viktor Yanukovych was ousted following widespread protests against his administration in February.

"It has the earmarks of a tragic mistake made by someone who had the capability to shoot down an aircraft and we know at least from the last few couple weeks that could be Russian or separatist-Russian capability. If that's true this is really, really something that commands our attention to bring this kind of thing to a halt in Ukraine," McCain said.

McCain also panned President Barack Obama's handling of the crisis in Ukraine and dismissed the latest round of sanctions against Russia, which the White House announced Wednesday.

"The United States has been insulting in how small and how little help we have given. I mean they have been begging us for defensive weaponry; we have not given it to them," McCain said. "The sanctions so far in exchange for Crimea have been minuscule. These latest enacted by the Obama administration I think are helpful but if you ask the Ukrainian government that's struggling, they said they need weapons in which to defend themselves."

After his appearance on MSNBC, McCain's office released a statement urging the immediate supply of antitank and anti-air weapons to Ukraine.

"It is shameful that the administration continues to refuse to provide our Ukrainian partners with the military capabilities they both want and need," he said.

