Following Thursday's news, Sen. Kelly Ayotte, R-N.H., urged reconsideration of adding military aid to a $1 billion package already sent to Ukraine this spring.
"Ukrainians need assistance--and not only the sanctions the administration has issued, which could get tougher but they need military assistance from our country," she said. "They are not asking us to send our troops in. They are not asking for things like that. They are willing to defend themselves and they need our help to do so. "
Prevailing theories a day after the crash suggest the missile that brought down Flight MH17, killing all 298 people abroad, was fired from areas controlled by pro-Russian separatists.
Russian President Vladimir Putin has tried to downplay his government's support of rebel groups, but U.S. Ambassador to the U.N. Samantha Power noted the complex nature of the surface-to-air missile system and said "we cannot rule out" that Russian military were directly involved in training separatists to fire it to bring down a plane.
In her speech before the U.N. Friday, Power said separatists have previously taken credit for downing a transport plane, a helicopter and a cargo plane, and did the same following yesterday's strike, believing the Malaysian jet to be another Ukrainian cargo carrier. They later deleted the tweet taking credit.
Sen. John McCain, R-Ariz., has been a frequent proponent of U.S. military intervention in Ukraine and elsewhere and called it a "cowardly" mistake to fail to send in weapons.
"If we had given them weapons, perhaps they could have taken that part of Ukraine back and that attack [on MH17] never could have been mounted from what apparently was a base where they captured this anti-aircraft missile capability," he said. "And again, it takes training. This was not like one of those shoulder-fired missiles, this takes training and obviously that training came from Russia."
President Obama, speaking from the White House Friday, urged caution while condemning Russia for refusing "to take the concrete steps necessary to de-escalate the situation."
The president said he and his advisors "don't see" the U.S. ramping up direct military role beyond ongoing work with NATO.
"I've made it clear to President Putin I would prefer to solve this diplomatically," he said.