WASHINGTON (Reuters) - U.S. Senator Bob Corker accused his fellow Republicans of being afraid to stand up to President Donald Trump on Tuesday, as his legislation to block the president’s ability to impose tariffs on national security grounds hit a roadblock in Congress.

“‘We might poke the bear’ is the language I have been hearing in the hallways,” Corker said in an emotional Senate speech. “The president might get upset with us as United States senators if we vote on the Corker amendment, so we’re going to do everything we can to block it.”

Corker and other lawmakers - Democrats as well as some of Trump’s fellow Republicans - introduced the measure last week after the president’s recent announcement that he was considering tariffs on automobiles, after imposing tariffs on steel and aluminum, citing national security concerns.

Trump, who campaigned on a pledge to negotiate better trade deals to bring back U.S. manufacturing jobs, has pursued aggressive measures against trading partners from China to Canada, Mexico and U.S. allies in Europe.

This has worried some lawmakers who strongly back principles of free trade, warning that Trump could trigger a trade war that would destabilize the economy and ultimately hurt American workers.

Corker’s amendment would have pared back Trump’s authority under Section 232 of the Trade Expansion Act of 1962 to impose tariffs on national security grounds without obtaining Congress’ consent.

Its backers had hoped for a Senate vote as soon as this week by including the legislation as an amendment to the National Defense Authorization Act for 2019, or NDAA, a sweeping defense policy bill that Congress passes every year.

But Senator James Inhofe, the Republican who is managing debate on the defense bill, blocked the amendment as inappropriate for the legislation, preventing a vote.