Coca-Cola is committed to collecting and recycling plastic bottles rather than switching to aluminium cans as the world's largest soft drinks maker seeks to reduce its carbon footprint, its chief executive officer told Reuters.

Along with multinational rivals including PepsiCo and Nestle, Coca-Cola has started offering recyclable aluminium cans as well as plastic bottles for some water brands as the industry reacts to public outrage over the world's oceans being polluted with plastic waste.

But Coca-Cola's launch of a range of cans for sparkling water in the United States is not part of a broader shift, said CEO James Quincey during an interview in Nigeria's commercial capital Lagos.

"We are not trying to engineer a strategic shift from plastic to aluminium," said Quincey, adding that the firm was "focused on collecting" and has a collection rate of about 59%.

Quincey said import tariffs of 25% on steel and 10% on aluminium that US President Donald Trump set in 2018 to preserve national security would also not alter its plan.

"It's not so big that it's going to make us change our strategy," said Quincey on the impact of the tariffs.

"Given the relative weight of aluminium in our total business, it hasn't caused a big change in strategy - just a cost increase that fed through to the consumers," he said.

Last year Coca-Cola pledged to collect and recycle a bottle or can for every one it sells globally by 2030.

The company adopts different methods around the world to collect bottles. In some countries it uses a deposit return scheme that enables consumers to return bottles in exchange for incentives - such as cash, vouchers or a points-scheme. It also works with private firms that employ collection agents to retrieve used bottles.

"A recycled PET (polyethylene terephthalate) bottle has a much lower carbon footprint than an aluminium can or a returned glass bottle," said Quincey.

He said collecting and reusing bottles was a "better long term answer" than switching to cans.

Last month environmental group Greenpeace said Coca-Cola was the world's biggest producer of plastic waste for the second year in a row.

Working with the Break Free From Plastic movement, it said 11 732 branded Coca-Cola plastics were recorded in 37 countries - more than the next three top global polluters combined.

But Coke's CEO said this was just a reflection of the drinks company being the "biggest brand".

Coca-Cola beat Wall Street estimates with quarterly revenue of $9.51 billion last month, prompting the company to give an upbeat forecast for 2019.