The United States posted weaker-than-expected job growth in June as new data showed the labor market is facing headwinds ahead of testing midterm elections for President Donald Trump's Republicans.Total nonfarm payroll employment grew by 57,000 and the unemployment rate fell slightly to 4.2 percent, the US Bureau of Labor Statistics (BLS) said in a statement on Thursday.

After months of seesawing growth and contraction, the US job market posted strong gains in the last three months – but Thursday's data revised some of those numbers down.

Employment in April and May were revised down by 74,000 jobs, the BLS said.

June's data badly missed market expectations, with economists polled by Dow Jones Newswires and the Wall Street Journal expecting growth of 115,000 jobs.

Nevertheless, job growth remained in positive territory, with the US Federal Reserve not expected to intervene on the labor side of its mandate.