US House Speaker Nancy Pelosi has stressed that Washington's policy on Taiwan remains unchanged after her Taiwan visit brought about a sharp response from China.

Pelosi spoke to reporters on Friday in Tokyo, where she is making a two-day visit on the last leg of her Asia tour.

Before coming to Japan, she visited Taiwan as the first sitting US House speaker to do so in 25 years.

Pelosi said, "The Chinese have tried to isolate Taiwan" but "our friendship with Taiwan is a strong one." She added that "we will not allow them to isolate Taiwan."

China is conducting large-scale military exercises near Taiwan following her visit.

Pelosi said Beijing is "probably using our visit as an excuse" and reiterated that "our representation here is not about changing the status quo."

When a reporter mentioned speculation that her trip to Taiwan was more about burnishing her own legacy, the speaker replied that it was about Taiwan and its people.

Asked about how her visit will affect US-China relations, Pelosi said it doesn't determine what the bilateral relationship is, calling it a "much bigger and longer-term challenge."

She said "if we do not speak out for human rights in China because of commercial interests, we lose all moral authority to speak out about human rights any place in the world."

But she added that "we must work with China" on climate change and other issues.

As for her meeting with Japanese Prime Minister Kishida Fumio on Friday, Pelosi said "we had a very positive meeting about our friendship" and "shared our views."