The brand has released its first official image of the car in the form of a rendered view of its interior. It takes clear influence from the latest A-Class, with a large combined digital instrument and infotainment display above AMG GT-style air vents.
The GLB, sitting above the GLA and below the larger GLC, will be a fully fledged rival to cars such as the BMW X1, Audi Q3, Volvo XC40 and Jaguar E-Pace. The concept version appearing in the coming weeks will be close to production spec, with the finished car making its public debut at the Frankfurt motor show in September.
Alongside regular variants, a hot AMG 35 variant was recently spotted testing. Visual differences include larger wheels to house uprated brakes, a larger air intake on the lower front bumper and a redesigned grille pattern echoing that of other AMG models.
The design of the rear bumper has also been revised to allow for the addition of a dual-exit exhaust system, while the car's lower stance hints at a sportier suspension set-up.
Using the same 2.0-litre mild hybrid petrol engine found in the new A35 hot hatch, the GLB 35 will produce around 302bhp. It will be joined by a range-topping GLB 45 after launch.
Previous images showed the GLB lapping the Nürburgring Nordschleife in standard form.
Due to arrive in showrooms before the year is out, the GLB mixes old-school G-Class influences, including a boxy profile and an upright rear end, with contemporary details, such as the brand's softer front-end design and LED headlights.
The line-up will feature an updated range of Mercedes/Renault-Nissan four-cylinder petrol and diesel units, producing upwards of 160bhp. Also planned is a petrol-electric plug-in hybrid variant with a modest electric-only driving range.
Development of the long-mooted GLB has been accelerated in order to bring the car to market this year.
The move is part of Mercedes’ plan to retain sales momentum in the lucrative premium compact car class.