Republic of China officials are holding their tongues in response to reports that President Trump has held up a $400 million arms sale to the Taiwan-based government, prompting fears that the deal could become a pawn in trade negotiations between Washington and Beijing.

The Washington Post reported on Friday that Mr. Trump had declined over the summer to sign off on the previously approved sale of the weapons, which the Post said would have been “more lethal” than past rounds of aid to Taiwan, including munitions and autonomous drones. It said the decision could still be reversed.

The report, which cited  “five people familiar with the matter” as sources, appeared on the same day that Mr. Trump spoke by telephone with Communist Chinese President Xi Jinping in an effort to close a deal for the transfer of the video app TikTok to U.S.-controlled ownership. Plans for Mr. Trump to visit Beijing next year were also announced.

Authorities in Taipei, which lives with the constant threat of an invasion from mainland China and relies heavily on America for weapons, have so far issued only vague remarks in response to the Post report.

The island’s defense ministry issued a statement saying, “Taiwan and the U.S. maintain a close security cooperation mechanism, with all exchange programs carried out on schedule to build a comprehensive defense system.”

President Lai Ching-te, for his part, was quoted Saturday saying simply, “To avoid war and defend peace we must build defense capabilities and societal resilience through continued preparedness.”

The future of Taiwan, which mainland China claims as a wayward province that must be brought back into the fold, is one of the most delicate issues in U.S.-China relations and Beijing invariably objects to American military assistance to the ROC government.

That has prompted speculation in some circles that the weapons sale could become a bargaining chip in Mr. Trump’s months-long effort to conclude a broad agreement with Beijing covering investment, trade, and tariffs, as well as the sale of TikTok.

“The decision has not yet been finalised, but it underscores how the Trump administration is weighing Taiwan’s security needs against its efforts to secure a trade agreement with China,” reported Invezz, a business-oriented publication with editorial offices in London.

“The move comes just as Trump prepares for his first phone call with Chinese President Xi Jinping since June, signalling how military and trade considerations are increasingly being negotiated together.”

Mr. Trump later described that two-hour conversation with Mr. Xi as “very productive,” saying the two had “made progress on many very important issues including Trade, Fentanyl, the need to bring the War between Russia and Ukraine to an end, and the approval of the TikTok Deal.”

He also announced plans for a face-to-face meeting with Mr. Xi at the APEC Summit in South Korea at the end of October and plans to visit Communist China early next year. He said Mr. Xi would pay a reciprocal visit to America at “an appropriate time.”

Despite early optimism that the TikTok deal would be concluded in the Friday conversation, White House officials indicated that more work remains to be done.

That deal “is well on its way, as you know, and the investors are getting ready,” Mr. Trump said according to a pool report. “We have to get it signed … I guess it could be a formality.”