Despite disappointing job growth last month, the unemployment rate fell to its lowest level since early 2008, sharpening the debate within the Federal Reserve over whether to raise interest rates when policy makers meet in two weeks.

Friday’s report from the Labor Department — which found that employers added a weaker-than-expected 173,000 jobs in August while the official jobless rate dipped to 5.1 percent — provided fodder for both camps to make their cases.

The slowdown in job growth and the absence of any significant wage pressure could strengthen the arguments of those who see little risk in keeping borrowing costs exceptionally low and waiting not just for more encouraging data but also for unruly markets to settle down.

On the other side, there were enough positive indicators to keep a September tightening in play, even as Wall Street looks more seriously at the possibility of a Fed move in October or at the central bank’s last meeting of the year, in December.