McLaren racing director Eric Boullier has suggested that the team could endure another tough weekend at the Belgian Grand Prix.

Since changing to Honda engines, the Woking-based outfit have largely struggled for pace and reliability, but are expected to roll out new engine upgrades at Spa Francochamps next weekend.

However, Boullier has said that McLaren are not realistically aiming to make an impact until Singapore next month.

"Spa is a truly spectacular circuit, arguably the best on the calendar for many, but given the unique power and downforce package required the track won't play to our strengths," Boullier told reporters.

"Therefore, of course, we must be measured in our optimism, and we will need to wait for Singapore and beyond before we can see the fruits of our labours reflected on track."

McLaren are currently ninth in the constructors' championship.