Munich-based BMW said on Thursday that sales of its core brand rose 13.5 percent in July to 128,594 vehicles, compared with Audi's 9.8 percent gain to 131,300.
BMW's global deliveries already fell behind Audi's in January and April. BMW's year-to-date sales lead over Audi, which contributed about 40 percent of VW's 3.43 billion-euro ($4.57 billion) group profit in the second quarter, eased slightly to 21,000 cars from 24,000 after six months.
BMW's annual lead over Daimler's (DAIGn.DE) Mercedes-Benz totaled 122,000 vehicles, although third-ranked Mercedes last week reported a 20-percent surge to 116,790 cars.
Audi eclipsed Mercedes-Benz in 2011 as the world's No. 2 luxury carmaker. Audi and Mercedes are both aiming to replace BMW in the top spot by the end of the decade.
"The three premium makers are closing ranks," said Frankfurt-based Commerzbank analyst Sascha Gommel, accrediting the strongest momentum to Mercedes thanks to a raft of new models. "The battle is heating up."
Sports-car manufacturer Porsche, another VW division, said on Thursday that global sales rose 11 percent to 13,731 autos, powered by demand in the United States and China.
The maker of the iconic 911 model posted double-digit growth in its German home market, just like BMW, in another sign that Europe's No. 1 sales region may be headed for recovery.
Registrations of new cars in Germany rose 2.1 percent to 253,146 vehicles last month, the Federal Motor Transport Authority (KBA) said on Wednesday.
Reporting by Andreas Cremer; editing by Tom Pfeiffer