China declined a US request for Secretary of Defense Lloyd Austin to meet his counterpart Li Shangfu in Singapore this week, part of what the Pentagon called a “concerning unwillingness” to engage in military discussions.

The Defense Department “believes strongly in the importance of maintaining open lines of military-to-military communication between Washington and Beijing to ensure that competition does not veer into conflict,” Pentagon Press Secretary Brig. Gen. Pat Ryder said in a statement Monday.

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The US had proposed in May that the two defense officials meet at the Shangri-La Dialogue that’s set to take place in Singapore. China demanded that the US lift sanctions that were imposed on Li in 2018 over the role he played overseeing an arms purchase from Russia.

China had argued that Li wouldn’t be on equal footing with Austin if the sanctions stayed in place, Bloomberg News reported earlier.

The rejection is latest rebuff of US efforts to strengthen military communications with China, although the two nations are taking tentative steps toward getting bilateral ties back on track after an alleged Chinese spy balloon crossed US territory earlier this year.

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The US sanction designation “does not prevent Secretary Austin from meeting with him in the course of conducting official United States Government business,” Ryder said.