German Chancellor Olaf Scholz praised US Vice President Kamala Harris as a "competent and experienced" politician who could well win the US election, but he stopped short of endorsing her over Republican Donald Trump.

Scholz had been unusually direct in his endorsement of US Joe Biden before the latter dropped his reelection bid last weekend and endorsed Harris as the Democratic Party's candidate to face Trump in the November election.

Many German politicians fear Trump could impose higher tariffs on imports if he returned to office, and they have raised questions about US support for the NATO military alliance.

Germany was frequently the focus of Trump's ire during his first term due to its trade surplus with the United States and low spending on defence. Berlin has however in recent years upped its defence spending.

"The election campaign in the USA will certainly be exciting, now with a slightly new line-up and a new constellation," Scholz told an annual summer news conference on Wednesday.

"I think it is very possible that Kamala Harris will win the election, but the American voters will decide."

Scholz said he had met Harris several times.

"This is a competent and experienced politician who knows exactly what she is doing," he said. "She knows what she wants and what she can do."