A U.S. air force jet that flew House of Representatives Speaker Nancy Pelosi to Malaysia left the country on Tuesday and flew close to the Philippines, in the day's most followed flight on tracking site Flightradar24.
Reuters could not immediately establish if Pelosi or her delegation were on flight SPAR19, but authorities in the Philippines, a U.S. ally, said no request had been received from the United States for her to visit or transit in the country.
The plane left Kuala Lumpur at 3:42 p.m. (0742 GMT) and flew east towards Borneo on a route that skirted the South China Sea.
It was last seen on the tracker off the southernmost Philippine region of Mindanao, however, flying along the country's Pacific east coast.
Pelosi was expected to arrive in Taipei later on Tuesday, sources said earlier.
Like SPAR19, a second U.S. air force plane arrived in Kuala Lumpur on Tuesday morning. According to Flightradar24, SPAR20 had not left the Malaysian capital.
A visit to Taiwan by Pelosi, who is second in the line of succession to the U.S. presidency and a long-time critic of China, would come amid worsening ties between Washington and Beijing.
She has not confirmed if she would visit the self-governed island which Beijing claims as its own.
Both the Philippines air force and its Department of Foreign Affairs (DFA) said they had received no word from the United States that Pelosi might land in the country on Tuesday.
"The DFA has not received any request from the U.S. government or their embassy in Manila for Speaker Pelosi to transit and/ or visit the Philippines as part of her current swing of visits to the region," the DFA said in a text message to reporters.
As of 1130 GMT, SPAR19 was flying just south of the Philippines, according to Flightradar24, in a route tracked by as many as 300,000 people on its website.
A normal flight from Kuala Lumpur to Taiwan's capital of Taipei would cross the South China Sea, with a typical flight time of under five hours.
Since last week, China's People's Liberation Army has conducted various exercises, including live fire drills, in the South China Sea, Yellow Sea and Bohai Sea, in a show of Chinese military might. (Reuters)