Asda's US owner has said it is "seriously considering" a stock market flotation for the UK supermarket after the chain's deal to merge with rival Sainsbury's was blocked.

Walmart - the world's biggest retailer - told Asda managers it was mulling listing Asda, but that any preparations would "take years".

"While we are not rushing into anything, I want you to know that we are seriously considering a path to an IPO - a public listing - to strengthen your long-term success," Judith McKenna, Walmart's international chief executive said.

"Walmart does not have a one-size-fits-all approach to operating its international markets, but a consistent focus on strong local businesses powered by Walmart," she added. 

The comments come after Britain's competition watchdog ended Sainsbury's audacious £12 billion bid to merge with rival Asda earlier this month. 

The Competition and Markets Authority (CMA) vetoed the deal, saying it would lead to increased prices in stores, online and at petrol stations across the UK, with shoppers left "worse off" and quality affected.

The move has sparked speculation over Walmart's plans for Asda, with rumours it may try to sell the Big Four chain or spin it off.

Walmart bought Asda in 1999 for £6.7 billion. 

Asda has reported seven quarters in a row of like-for-like sales growth, but the big players are under pressure amid intense competition from German discounters Aldi and Lidl.

Asda's like-for-like sales rose 1% in its fourth quarter, with recent trading boosted by moves to slash prices, invest in own-brand products and improve its online service.