US job openings unexpectedly rose in September, highlighting enduring tightness in the labor market and risking sustained upward pressure on wages that will likely keep the Federal Reserve on a path of steep interest-rate increases.

The number of available positions increased to 10.7 million in September from a revised 10.3 million a month earlier, the Labor Department’s Job Openings and Labor Turnover Survey, or JOLTS, showed Tuesday. The median estimate in a Bloomberg survey of economists called for a drop to about 9.8 million.

The surprise pickup in vacancies highlights unrelenting demand for workers despite mounting economic headwinds. The persistent imbalance between labor supply and demand continues to underpin robust wage growth, adding to widespread price pressures and reinforcing expectations for yet another large rate hike on Wednesday.

The S&P 500 turned negative after the data, and Treasury yields pared declines.

The largest increases in vacancies were in accommodation and food services, health care, and transportation, warehousing and utilities.

The ratio of openings to unemployed persons rose in September. There are now some 1.9 available jobs for every unemployed person, compared with 1.7 in August.

Fed officials watch that ratio closely and have pointed to the elevated number of job openings as a reason to why the central bank may be able to cool the labor market -- and therefore inflation -- without an ensuing surge in unemployment.

Some 4.1 million Americans quit their jobs in September, little changed from a month earlier. The quits rate, a measure of voluntary job leavers as a share of total employment, held at 2.7%.

Hires fell to about 6.1 million from 6.3 million a month earlier.

--With assistance from Jordan Yadoo.

This article was provided by Bloomberg News.