WASHINGTON — President Barack Obama on Friday sacked a proposed regulation tightening health-based standards for smog.

Obama overruled the Environmental Protection Agency and directed administrator Lisa Jackson to withdraw the proposal, in part because of the importance of reducing regulatory burdens and uncertainty for businesses at a time of rampant uncertainty about an unsteady economy.

The announcement came shortly after a new government report on private sector employment showed businesses essentially added no new jobs last month, and the jobless rate remained stuck at a historically high 9.1 percent.

A spokesman for House Speaker John Boehner, R-Ohio, had muted praise for the White House, saying that withdrawal of the smog regulation was a good step toward removing obstacles that are blocking business growth.

Criticism from environmentalists was swift. “The Obama administration is caving to big polluters at the expense of protecting the air we breathe,” said Gene Karpinski, the president of the League of Conservation Voters. “This is a huge win for corporate polluters and huge loss for public health.”