By Adam Smith
TPP, though pushed by former U.S. President Barack Obama, became politically toxic by the 2016 election, with President Donald Trump calling the deal "another disaster done and pushed by special interests who want to rape our country, just a continuing rape of our country."
But Khanna said the U.S. will lose out.
"The U.S., by not joining TPP, will prove to be a seminal error as the White House miscalculated in believing it would not move forward without the US, but it very much has," said Khanna, who holds a doctorate from the London School of Economics.
While the partnership kicked off two weeks ago with New Zealand, Australia, Canada, Japan, Mexico and Singapore, it will grow in the months to come as Brunei Darussalam, Chile, Malaysia and Peru will join in, following Vietnam's entrance this week.
In the short term, he said, Canada, Japan and other US trade partners are "focusing on taking American market share in the region in agriculture, industrial exports, consumer goods, and so forth."
But in the longer term, he said, trade partners will see the U.S. as "unreliable."