US president Donald Trump's wide-ranging tariff policies have upended global trade and fuelled inflation. (EPA Images pic)WASHINGTON: The United States posted strong economic growth in the third quarter, but the Fed's preferred inflation gauge also accelerated, the commerce department said on Thursday, in a mixed economic bag for US president Donald Trump ahead of key midterm polls next week.

Real GDP increased at an annual rate of 3.4% in the third quarter, the department's Bureau of Economic Analysis (BEA) said in a statement, beating market expectations.

"The contributors to the increase in real GDP in the third quarter were increases in investment, consumer spending, and government spending that were partly offset by a decrease in exports," the BEA said in a statement.