U.S. President Donald Trump formally withdrew the United States from the Trans-Pacific Partnership trade deal on Monday, distancing America from its Asian allies as China's influence in the region rises.

Fulfilling a campaign pledge to end American involvement in the 2015 pact, Trump signed an executive order in the Oval Office pulling the United States from the 12-nation TPP.

"Great thing for the American worker," Trump said as he signed the order on his third full day in office. The Republican says the trade deal would have damaged U.S. manufacturing.

The accord, backed heavily by U.S. business, was negotiated by former President Barack Obama's administration but never approved by Congress. It had been the main economic pillar of the Obama administration's "pivot" to the Asia-Pacific region to counter China.

Trump has sparked worries in Japan and elsewhere in the Asia-Pacific with his opposition to the TPP and his campaign demands for U.S. allies to pay more for their security.

Harry Kazianis, Director of Defense Studies at the Center for the National Interest think tank in Washington, said Trump must now find an alternative way to reassure allies in Asia.

"This could include multiple bilateral trade agreements. Japan, Taiwan and Vietnam should be approached first as they are key to any new Asia strategy that President Trump will enact," he said.

Sen. John McCain, R-Ariz., said abandoning TPP was the "wrong decision" and a "serious mistake that will have lasting consequences for America's economy and our strategic position in the Asia-Pacific region."

"This decision will forfeit the opportunity to promote American exports, reduce trade barriers, open new markets, and protect American invention and innovation. It will create an opening for China to rewrite the economic rules of the road at the expense of American workers. And it will send a troubling signal of American disengagement in the Asia-Pacific region at a time we can least afford it," said McCain, chairman of the Senate Armed Services Committee.

McCain emphasized the importance of a "positive trade agenda" in the Asia-Pacific region that keeps America "competitive in one of the most economically vibrant and fastest-growing regions in the world."