The United States added 192,000 jobs in March as private employers boosted hiring, a sign of improving strength in the economy, Labor Department data showed Friday. The jobless rate remained unchanged from February at 6.7 percent as the number of unemployed held steady at 10.5 million. The March job growth was a shade below analysts' average estimate of 195,000 net new jobs. But the overall picture showed stronger gains in the first quarter, despite severe winter weather, than previously estimated. The department upwardly revised job growth for January and February by a combined 37,000. All of March's job growth was in the private sector, but the number of private nonfarm payrolls added came in well below the 205,000 anticipated. Still, the March pace of job creation was better than the average of 183,000 over the prior 12 months. The jobless rate had been expected to dip back to 6.6 percent, the level seen in January.