Lin Fei-fan and Hsu Szu-chien, both deputy secretaries-general of Taiwan's National Security Council and several of their staff have traveled to the Washington area for meetings through this week, the sources said on condition of anonymity.

Reuters was not able to confirm who from the U.S. side would join the meetings or the agenda.

Taiwan's de facto embassy in Washington, China's embassy and the Trump transition team did not respond to requests for comment.

The visit by Lin and Hsu comes as China's military has stepped up activity near the Taiwan Strait, in what Taiwan has said is Beijing's effort to set a "red line" for the incoming Trump administration and U.S. allies.

One of the sources said the meetings were with individuals in Trump transition circles but would not include nominees for top positions in Trump's next administration, given sensitivity in Beijing over any talks between Taiwanese and U.S. officials.

The meetings are with "Republicans likely to populate mid-tier political positions" in the Trump administration, a second source said. A third source said it was "safe to say" Lin and Hsu were meeting the Trump transition team.

The United States does not have formal diplomatic relations with Taiwan, a self-governing island that China claims as its own territory. Taiwan rejects Beijing's sovereignty claims, saying only the island's people can decide their future.

HOPE AND WORRY IN TAIWAN

Trump's electoral win in November has sparked hope in Taipei that he will pursue a tough line with China but also anxiety given his comments that the island should pay the U.S. for its defense.

Trump has named numerous China hawks to key posts in his incoming administration, including Senator Marco Rubio as Secretary of State, who has called for unfettered interaction between U.S. and Taiwan officials.

Those nominations have been encouraging for Taipei, which Reuters has reported may place large new arms deals to show it takes seriously Trump's statements that Taiwan should pay "protection" money to the United States.

Engagement to date between Taiwan and the incoming administration appears to fall in a gray area of unofficial contact and has been low-key. That's a departure from the period before Trump's first term, when in December 2016, the month before his inauguration, he held a phone call with then-Taiwan president Tsai Ing-wen.

That call marked the first time since 1979 that a U.S. president-elect had spoken with the island's president, a move that angered China.

Ahead of his second inauguration, scheduled for Jan. 20, CBS News reported on Wednesday that Trump had invited Xi to attend the event, something that would be unprecedented for a Chinese leader.

The president-elect's camp and China did not immediately respond to a request for comment on the report, but Trump said in a interview with NBC News conducted last Friday that he "got along with very well" with Xi and that they had "had communication as recently as this week."