China has declined a request by the US for a meeting between their defence chiefs at an annual security forum in Singapore this weekend, media reported on Monday, a new sign of strain between the powers.

“Overnight, the PRC informed the U.S. that they have declined our early May invitation for Secretary Austin to meet with PRC Minister of National Defence Li Shangfu in Singapore,” the Pentagon said in a statement to the Wall Street Journal, referring to China by the initials of its official name, the People’s Republic of China.

The Pentagon said it believed in open communication “to ensure that competition does not veer into conflict.”

Last week, White House spokesman John Kirby said there were discussions by the Defence Department to get talks going between Lloyd Austin and his Chinese counterpart, who was named defence minister in March.

The prospect of a meeting between them was being closely watched given regional security tensions and trade disputes that have derailed plans for re-engagement by the world’s two largest economies.

Last week, US Commerce Secretary Gina Raimondo and Chinese Commerce Minister Wang Wentao traded barbs on trade, investment and export policies in a meeting in Washington that marked the first U.S.-China cabinet-level exchange in months.

Singapore-based security analyst Ian Storey said China’s decision to shun Austin did not bode well.

“At a time of rising US-China tensions, General Li’s refusal to meet his American counterpart will fray regional nerves even further,” Storey said.

Austin and Li will be in Singapore to attend the annual Shangri-la Dialogue that opens on Friday, an informal gathering of defence officials and analysts that also plays host to a string of side meetings.

Both are expected to hold bilateral meetings with counterparts from around the region.

Chinese officials have yet to explain Li’s snub but some security analysts said Beijing’s annoyance at U.S. sanctions against him was a possible reason.

Li, who security scholars say is a veteran of the People’s Liberation Army modernisation effort, has been under U.S. sanctions since 2018 over the purchase of combat aircraft and equipment from Russia’s main arms exporter, Rosoboronexport.

Li is a member of the Central Military Commission, China’s top defence body that is commanded by President Xi Jinping.