Washington ( CNN ) -- President Obama 's plan to train and arm Syrian rebels in their battle against ISIS fighters faces deep skepticism from a large number of Democratic senators who will vote Thursday whether to approve the escalation of U.S. involvement in the deadly conflict . While Senate leaders are confident the measure will pass , misgivings raised by so many senators from the President 's party speak to the difficulty the administration is having gaining traction for its ISIS policy . It also suggests an upcoming debate in November over whether to OK broader military action against ISIS could be contentious . House approves plan to assist Syrian rebels . Democrats have a 55-45 majority in the Senate ( 53 Democrats and two independents who caucus with the party ) . In a floor speech Wednesday , Sen. Joe Manchin , a centrist Democrat from West Virginia , cited reports that some of the moderate Syrian rebels the United States wants to arm had sold the American journalist Steven Sotloff to ISIS , which murdered him . `` Are those people our allies ? '' he asked . `` I strongly believe that if our military arms and trains Syrian rebels , we will be involving ourselves in a ground conflict we can not resolve , where potentially everyone involved is our enemy , '' Manchin said . `` There are a lot of people struggling with this vote right now , '' said Sen. Chris Murphy of Connecticut . `` I really have no idea what the ultimate vote will be . '' Murphy , a freshman Democrat , is a leading critic of arming the rebels . He fears the weapons one day will be turned on Americans . `` I think it 's very hard to sort out the moderate rebels from the extremists and I have a real worry that once we send these rebels back into the battle space there is very little we can do to prevent them from locking arms with al Qaeda or elements of ISIS , '' Murphy explained . Sen. Mark Begich , an endangered Democratic running in a tight re-election in Alaska , said he is unhappy the serious question about the Syrian rebels will be tucked inside a large government funding bill -- known as a continuing resolution , or CR -- and is not likely to face a up or down vote by itself . `` They should n't wedge this issue into the CR . This is an important issue to determine our role in the Mideast . For them to just throw it into the budget bill is a disservice to the American people , '' Begich said as he left a vote on the Senate floor Wednesday . Begich , like Murphy , said he supports other aspects of the President 's policy to defeat ISIS -- including airstrikes -- but is concerned the weapons the United States provides the Syrians will `` end up in someone else 's hands that are not our friends . '' Other Democrats in tough re-election campaigns have struggled to make up their minds . `` I support the intent but I want to see the ( legislative ) language , '' Sen. Jeanne Shaheen of New Hampshire said . Asked which way he would vote , Sen. Mark Udall of Colorado told CNN he was undecided and `` looking at the language right now '' as he hustled to the Senate floor for a vote . Minutes later as he left the Capitol , he told CNN he intends `` to vote for the President 's plan to arm the rebels . '' Even Dick Durbin , the second-ranking Senate Democrat , could n't say whether he would vote yes . `` There are some aspects of it I think need clarity , '' he said as he rode a subway car to a Senate office building to listen to Secretary of State John Kerry testify on ISIS before the Foreign Relations Committee . `` I want to wait and see . I think it 's only fair to the people I represent and the President . '' Sen. Claire McCaskill , D-Missouri , a member of the Armed Services Committee , pushed back on critics of the President 's plan . She said the U.S. intelligence community will play an important role in vetting the rebels and that training could take up to a year before arms are provided . `` All of those people criticizing this choice , I have yet to hear their better idea , '' she said . Despite the lukewarm reception the President 's plan has gotten from many Democrats , Sen. Chuck Schumer of New York , the third-ranking Senate Democrat , predicted it will pass . `` I think on the ISIS bill , while everyone is worried and has concerns , the President 's proposal has broad support and I think you 'll probably find a majority of Republicans and majority of Democrats voting for it , which in this place at this time is a rare thing , '' he said .
House votes to continue arming and training Syrian troops . Democratic - led Senate votes on the bill Thursday . Many Democrats are skeptical and believe the effort could lead to a slippery slope . It will be tucked inside a larger spending bill .