UPDATE 1-Carrefour Q3 sales slow, on the offensive despite failed Auchan tie-up

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PARIS, Oct 20 (Reuters) - Carrefour, which earlier this month ended talks over a possible tie-up with unlisted rival Auchan, said it remained on the offensive as it kept a guidance for 2021 net free cash flow "comfortably" above 1 billion euros.

Europe's largest retailer also said revenue growth slowed in the third quarter, reflecting weaker sales in the core French market where a mandatory COVID-19 health pass hit business at its large out-of-town hypermarkets.

"With its robust balance sheet, and thanks to the commitment of its teams, Carrefour is attractive and on the offensive, for the benefit of its customers and its shareholders,” Chairman and CEO Alexandre Bompard said in a statement.

Earlier this month Carrefour and Auchan ended talks over a possible partnership, the second time this year Bompard's plans to create a Gallic supermarket powerhouse have been frustrated.

Carrefour is in the midst of a five-year plan it launched in January 2018 to cut costs and boost e-commerce investment to improve profits and sales, as it seeks to tackle competition from online rivals such as Amazon and discounters like Lidl or unlisted retailer Leclerc.

Carrefour said sales reached 20.468 billion euros ($23.83 billion) in the third quarter, a like-for-like rise of 0.8% but a slowdown from 3.6% growth in the second quarter.

In France, where Bompard has made reviving flagging sales at hypermarket stores a priority, sales eased 0.3% following a 4.% rise in the second-quarter.

French hypermarket sales alone fell 2.8% in the quarter after rising 4.3% in the second quarter.

The introduction in France in August of a health pass that customers have to show in shopping malls with a surface area of more than 20,000 square metres (215,278 sq ft) hit business in the third quarter at the hypermarket stores. ($1 = 0.8588 euros)

(Reporting by Dominique Vidalon Editing by GV De Clercq, William Maclean)