Two House Republican leaders stood firm on Thursday that Greece should not receive aid from the International Monetary Fund despite a dramatic drop in the U.S. stock market caused in part by concern over Greece's uncertain financial future. The Dow Jones Industrial Average dropped 900 points at one point Thursday afternoon, according to media reports. It later rebounded, closing down about 350 points. House Republican Conference Chairman Mike Pence (Ind.) and Conference Vice Chairwoman Cathy McMorris Rodgers (Wash.) suggested the drop was evidence that investors were concerned that a Greek "bailout" was on the horizon. "The American people deserve to know that American taxpayers will be on the hook for 17 percent of the IMF's portion of this Greek bailout," Pence said. He said he and McMorris Rodgers would continue to do their "level best to call on the administration to use all the powers at its disposal to ensure that U.S. taxpayer dollars are not used to bail out Greece." Last week, Pence and McMorris Rodgers urged the Obama administration to block any "American taxpayer-funded bailouts" of Greece in a letter to Treasury Secretary Timothy Geithner. Greece has been struggling for months to get a handle on its debt crisis. The European Union and the IMF have offered Greece a $140 billion package to shore up its limping economy.