Analysts say Abe, who had spent considerable political capital to have TPP approved at home, hopes the U.S. will re-enter the agreement someday.
"Everyone talks about a vacuum in leadership and everyone talks about China filling that vacuum," said Wendy Cutler, a top Obama administration trade negotiator who worked on the TPP. "In this instance, it's Japan filling that role."
"You have these multiple paths to establishing the rules of trade and better integration of trade within Asia, and then you have the U.S., the outlier," said Robert Holleyman, a Washington attorney and former deputy U.S. trade representative.
Holleyman was in Vietnam recently for meetings before of the Asia-Pacific Economic Cooperation summit Friday in Da Nang, which Trump will attend. What Holleyman said he kept hearing was a "consistent theme from other APEC economies that said, essentially, 'Now that the U.S. has left Asia, we need to step forward and do this on our own.'"
"As an American, I hated to hear those comments. They were saying it as a matter of fact," he said.
An economically sidelined U.S. in Asia would almost certainly weaken American companies and hurt exports, particularly of farm goods, and the prospects for returns on the huge investments that U.S. firms have made throughout the region over the past 35 years, trade experts say. U.S. firms may face higher duties and other more onerous barriers than they would have if trade agreements that included America were in place.
Many in Asia and America still see the U.S. as an economic superpower in the region, and they may have found some encouragement in how Trump has toned down his trade rhetoric during his trip thus far.
Asian leaders will listen closely to the speech Trump is scheduled to give Friday to American business leaders accompanying him on his tour. He is expected to use the speech to outline U.S. involvement in the Indo-Pacific region, a reference that is meant to include India, the world's largest democracy.
The U.S. Chamber of Commerce, which has clashed with the Trump administration on the North American Free Trade Agreement and trade policy more generally, said it took heart from the fact that Trump regarded Asia as important enough to make a visit lasting nearly two weeks -- the longest of any American president in more than a quarter century.
But chamber officials also worry that Trump has yet to articulate a strategy for commercial engagement in the region. All that he has espoused is a consistent line that the U.S. wants fair and reciprocal trade to reduce America's large trade deficits with Asian countries and that he prefers negotiating bilateral deals rather than multilateral ones.