Washington ( CNN ) -- Top American officials harshly criticized Russia on Friday for its continued support of pro-Russian rebels in Ukraine following the downing of a Malaysia Airlines jetliner . President Barack Obama said Friday that Russian President Vladimir Putin has the `` most control '' over the situation in eastern Ukraine as intelligence indicates that rebels most likely shot down Flight 17 from an area they control with a surface-to-air missile . Nearly 300 people were killed in Thursday 's disaster , including one American . Obama said the rebels ' sophisticated weaponry and training needed to shoot down aircraft `` is coming from Russia '' and said the United States could ratchet up sanctions on Russia if it continues to support the rebels . But he stopped short of blaming Russia or Putin for the debacle in eastern Ukraine . But Senior Republican lawmakers , most outspoken on foreign affairs and often critical of Obama 's foreign policy , did n't hold back . They were quick and direct in blaming Putin and called for additional , more stringent sanctions against Russia . `` I think he is responsible , '' said Sen. John McCain , a member of the foreign affairs and homeland security committees . `` I mean , it was n't Vladimir Putin that pushed the button to launch the missile , but the whole scenario , including the buildup of Russian troops across the border ... I think that he gave them the material and wherewithal to do it -- or facilitated it . '' Those calls come after Republicans have criticized Obama for months for not taking a harder line on Russia or meeting Ukrainian demands for more military assistance as it battled rebels . But now McCain said he sees `` no separation '' between Putin and the Ukrainian rebels , calling that movement `` clearly orchestrated '' by Moscow . And U.S . Ambassador to the United Nations Samantha Power said investigators ca n't rule out the possibility that Russia may have helped the separatists operate the complex missile system . Power also emphasized the crucial role Russia has played in the conflict in Ukraine , as well as the role the country can play to bring peace to the region . `` Russia can end this war . Russia must end this war , '' she said . Sen. Mark Kirk of Illinois said he believes operating the missile system `` would need backup from a nation-state like Russia . '' `` That would mean that Russian armed forces are directly involved in this wrongful death of roughly 300 people , '' Kirk asserted . Russian officials rebutted even the suggestion of Russian involvement and instead blamed Ukraine for creating a volatile environment in eastern Ukraine . And while there are conflicting reports over whether the plane 's flight data and cockpit voice recorders have been taken to Russia , Russian Foreign Minister Sergey Lavrov said Moscow would `` insist on the most objective , most open and independent investigation '' into the incident . Still , Kirk called for the Justice Department to file a wrongful death lawsuit `` against Russian assets in the U.S. '' and said the United States should target those assets to show Moscow that `` tens of millions of dollars will be lost . '' Rep. Peter King , a member of the House Homeland Security Committee , drew similar conclusions . He called Putin `` largely responsible '' for the downing of the passenger act , which Ukrainian officials have labeled as a terrorist act . `` If you 're a world power and you give this type of sophisticated weaponry to insurrectionists , you 're responsible for what happens after that , '' King said . `` This violates to me all norms of international behavior by a world power . '' U.S. officials have not yet concluded whether separatists obtained the missile system used to down the Malaysian airliner from Russia , though Obama confirmed that Russia has supplied heavy weaponry to the separatists . King said Russia 's arming of the rebels with sophisticated weaponry amounted to `` almost criminal negligence , '' even though he does not believe Putin wanted the passenger plane to be downed . And though the tragedy came a day after additional U.S. and European Union sanctions were leveled against Russia , McCain , King and other Republican lawmakers renewed calls for tougher sanctions . As retribution , King said the United States should consider further action such as preventing the Russian airliner Aeroflot from landing at U.S. and other Western airports . And King claimed such a ban would have a `` devastating effect on the Russian economy . '' King 's comments came after Oklahoma Republican Rep. Tom Cole called for a `` stronger response '' during an interview with CNN because `` pinprick sanctions are n't going to get the job done . '' Cole also called for direct military assistance to Ukraine , which he said is `` fighting for its survival . '' That 's a request the Kiev government has voiced to officials in Washington , asking for armament and military advice . `` I think that 's an unmistakable sign that we 're going to support them , that we 're going to try to give them the wherewithal to defend their territorial integrity . '' Even before U.S. officials confirmed the plane was shot down by pro-Russian separatists , Sen. Lindsey Graham , a South Carolina Republican , said Russian or separatist involvement would be a `` game-changer . '' Graham said that kind of information should trigger tougher sanctions from the United States and more support from other countries . Malaysian plane shot down in Ukraine : What happened ? Alleged phone call : 'We have just shot down a plane ' MH17 : Grief and mourning at Amsterdam 's Schiphol .
U.S. intelligence suggests pro-Russian separatists shot down Malaysia Airlines Flight 17 . President Obama said Putin has the `` most control '' over the situation in eastern Ukraine . Sen. John McCain and Rep. Peter King said outright that Putin is `` responsible '' `` Russia can end this war . Russia must end this war , '' the U.S . Ambassador to the U.N. said .