LONDON, Sept 18 (Reuters) - Asda, the British supermarket arm of Walmart, plans to enter the fast-growing convenience stores market through a trial with petrol forecourt operator EG Group, it said on Friday.

While Asda's sales have increased during the COVID-19 pandemic, it has lagged the growth of its big four rivals, market leader Tesco, Sainsbury's and Morrisons , partly because, unlike them, it does not have a convenience stores offer.

Local convenience stores have thrived during the crisis as Britons shop closer to home.

The convenience market is forecast to grow by 13.2% to 46.4 billion pounds in the three years to 2022, according to researcher IGD.

Asda's new convenience offer branded "Asda On the Move" will initially be trialled at EG Group fuel station forecourts in Ashby, Leamore and Primley in central England.

EG operates over 340 freehold-owned forecourt sites across the UK, giving plenty of scope for a roll-out.

Asda also said it would collaborate with home improvement group Kingfisher, trialing four "shop within a shop" compact B&Q stores within Asda superstores.

The first two will open in Dagenham, east of London and Sheffield, northern England later this year.

Asda also has partnerships with baker Greggs and delivery firm Uber Eats.

Walmart, whose attempt to sell Asda to Sainsbury's for 7.3 billion pounds was thwarted by Britain's competition regulator last year, is in talks with potential buyers of a majority stake in the supermarket chain.

($1 = 0.7724 pounds)

(Reporting by James Davey; Editing by Kirsten Donovan)