Hiring in the United States picked up pace in April and unemployment returned to the lowest level in decades, government data showed Friday, defying expectations of a slowdown despite higher interest rates. The latest figures show that the labor market remains strong despite banking sector upheaval, higher borrowing costs and uncertainty surrounding a potential government default. The world’s biggest economy added 253,000 jobs last month, up from a revised 165,000 figure in March, said the Labor Department. The jobless rate ticked back down to 3.4 percent, a level last seen in January and before then, the late 1960s. “Employment continued to trend up in professional and business services, health care, leisure and hospitality, and social assistance,” the Labor Department said in a statement. Average hourly earnings rose 0.5 percent to $33.36, data showed, and compared with a year ago, the figure is up 4.4 percent.