Ties which have often been rocky since Britain voted to leave the European Union in 2016 have been fortified by the countries' support for Ukraine since Russia's invasion.
"The partnership the UK and France share runs deep," Sunak said on Twitter.
"From tackling illegal migration to driving growth in our economies to defending our common security, when we work together we all benefit.
The Times newspaper said he would announce Britain was providing funding to France to invest in police, security and intelligence.
The payments were expected to exceed 200 million pounds over three years, the report said, citing unnamed sources.