The Scottish driver was just outside the top 10 on the free practice timing sheets at the Italian Grand Prix, but he told reporters on Friday that Q3 is within reach.
"The car seems to be relatively well balanced, but we've not been able to break into the top 10 yet," he admitted.
"So we need to work away tonight to try and improve things a bit more. Making Q3 is the big target, which is definitely achievable."
Di Resta qualified fifth at Spa last time out but almost snatched pole position as the drivers were initially struggling in changeable conditions.