A key U.S. factory gauge unexpectedly contracted for the first time since 2016, sending stocks and bond yields lower and boosting expectations for interest-rate cuts as global manufacturing woes deepen.

The Institute for Supply Management's purchasing managers index fell to 49.1 in August, weaker than all forecasts in a Bloomberg survey of economists, data released Tuesday showed. Figures below 50 indicate the manufacturing economy is generally shrinking. The group's gauge of new orders dropped to a more than seven-year low, while the production index hit the lowest since late 2015.

The data add to concern a broader U.S. recession is coming and may complicate the re-election chances of President Donald Trump, whose pledges to revive manufacturing have been a signature issue. At the same time, Trump's escalating tariffs on imports from China have been a major reason behind factory weakness that threatens to spread to consumer spending, which accounts for about two-thirds of the world's largest economy.