China has lavished investment pledges on Balkan states as it prepares for a summit with 16 EU countries and aspiring members, stoking fears in Brussels and influential national capitals of an effort to divide the bloc.

The gathering of the so-called “16+1” grouping in Sofia this week, just before the EU’s own summit with China this month, will be a fresh marker of Beijing’s ambitions in the region at a time of tension in Europe’s relations with Washington and Moscow.

One EU diplomat said Beijing’s response to bloc concerns that the 16+1 format “sucks up resources from the EU-China relationship” had been to bring the annual summit forward to barely seven months after the last one in Budapest. “The Chinese reaction was to press on the accelerator — a very typical reaction,” the diplomat said.