House Speaker Nancy Pelosi's visit to Taiwan only played in China's favor and assured that this would not have happened under him, former US President Donald Trump said, speaking at a gathering of conservatives in Texas.

He called his political opponent Pelosi, who twice impeached him, a woman who turns everything she touches into a bad thing.

"She fails. The women brings chaos. She played right into their hands, because now they have an excuse to do whatever they're doing," he said.

"And I will tell you it would have never ever happened in a million years under Trump, I can tell you." Trump said.