Chief executives at the largest U.S. companies are much more optimistic about their sales prospects than they were three months ago, though many remain cautious about hiring.

U.S. employers advertised more job openings in January, suggesting that hiring will remain healthy in the coming months.

A burst of hiring last month added 236,000 U.S. jobs and reduced the unemployment rate to 7.7 percent from 7.9 percent in January. The robust gains suggested that the economy can strengthen further despite higher taxes and government spending cuts.

The number of Americans seeking unemployment aid fell to a seasonally adjusted 340,000 last week, driving down the four-week average to its lowest level in five years. The drop is a positive sign ahead of Friday's report on February job growth.

A private survey shows U.S. businesses added a solid number of jobs in February, indicating higher taxes and looming government spending cuts have yet to slow hiring.

U.S. service companies grew in February at the fastest pace in a year, buoyed by higher sales, more new orders and solid job growth. The gain suggests higher taxes have yet to slow consumer spending on services.

U.S. manufacturers expanded in February at the fastest pace since June 2011, buoyed by increases in new orders and production. The third straight month of growth suggests factories may help the economy this year after slumping through most of 2012.

The number of Americans seeking unemployment aid fell 22,000 last week to a seasonally adjusted 344,000, evidence that the job market may be picking up.