China has become one of the largest bilateral infrastructure lenders to the Philippines, but its finance commitments swing wildly with the two countries’ fickle political relationship, a new report said, warning that lenders could shift focus as Beijing and Manila spar in the South China Sea.

China committed a total of $9.1bn in state-directed finance to the Philippines between 2000 and 2022, according to an investigation published on Wednesday by AidData, a research lab at William & Mary university.

The findings illustrate the special role China’s financial power plays in south-east Asia even as the region’s governments try to balance economic dependence on their large neighbour with their political and security interests. Successive governments in the Philippines, one of the oldest Asian allies of the US, have swung between Beijing and Washington.