President Donald Trump formally withdrew the U.S. from the Trans-Pacific Partnership (TPP) trade deal by signing an executive order on Jan. 23.

Fulfilling a campaign pledge to end American involvement in the 2015 pact, Trump signed an executive order in the Oval Office pulling the U.S. 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 said the trade deal would have damaged U.S. manufacturing.

The accord was negotiated by former President Barack Obama's administration, but was 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, D.C., 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.