With Democrats retaking control of the House of Representatives in Tuesday's U.S. midterm elections, Tokyo may see President Donald Trump accelerate his war on what he considers "unfair" trade with Japan, as he seeks ways to fire up his political base ahead of the 2020 presidential election, experts said.

In an election largely seen as a referendum on Trump's policies and leadership style, the midterms on Tuesday appeared to deliver a tempered rebuke of the president. Media polls showed Democrats were set to win a majority in the House, while Republicans were set to maintain control of the Senate.

"We believe the idea that the Japan-U.S. alliance is unshakable is shared by both parties, so I don't think the outcome of the poll will directly affect our bilateral relations," Chief Cabinet Secretary Yoshihide Suga said Wednesday.