President Barack Obama brought congressional leaders to the White House on Wednesday for the first time since a partial government shutdown began, but there was no sign of progress toward ending an impasse that has idled 800,000 federal workers and curbed services around the country. The standoff continued after a White House summit with chief executives as financial leaders and Wall Street urged a resolution before serious damage is done to the U.S. and world economy. Obama “refuses to negotiate,” House Speaker John Boehner, R-Ohio., told reporters after private talks that lasted more than an hour.