Republicans demanding concessions in exchange for raising the U.S. debt ceiling will be refused, the Democratic chairwoman of the Senate Budget Committee said on Friday. “We will not negotiate over whether or not the United States of America should pay its bills,” Senator Patty Murray said in a letter to colleagues. “And once again, before they get any further down this damaging path, we call on our Republican colleagues to not play politics with our economic recovery.” The United States is set to reach the debt ceiling in late February. Surging federal deficits and debt-limit fights have proven to be a double whammy, with the U.S. losing its top-tier credit rating from Standard and Poor’s in 2011. House of Representatives Speaker John Boehner said his fellow Republicans will not pass a debt increase without some concessions from Democrats. A few of the demands Republicans are considering include expanding offshore energy production, small changes in President Barack Obama’s healthcare law and approval of the Keystone XL oil pipeline. However, President Obama has vowed not to negotiate budget cuts to win passage of raising the debt limit. For investors, uncertainty reigns.