Talks to avert the year-end “fiscal cliff” appeared on the verge of an impasse Wednesday morning after late-night attempts to prevent negotiations from breaking down yielded no significant progress.

President Obama’s chief negotiator, Rob Nabors, rushed to the Capitol late Tuesday to meet with top aides to House Speaker John A. Boehner (R-Ohio) hours after the two leaders had a phone call described by Boehner in tepid terms.