One of America's most powerful labour unions is staging a protest against Amazon, aiming to put pressure on the tech giant as it rushes out packages in the final run-up to Christmas.

The Teamsters union said Amazon delivery drivers at seven facilities in the US had walked off the job on Thursday, after the company refused to negotiate with the union about a labour contract.

Teamsters members were demonstrating at "hundreds" of other Amazon locations, according to the union, which described it as the "largest strike" in US history involving the firm.

The company, which employs roughly 800,000 people in its US delivery network, said its services would not be disrupted.

"What you see here are almost entirely outsiders — not Amazon employees or partners — and the suggestion otherwise is just another lie from the Teamsters," Amazon said in a statement.

It was not clear how many people were participating in Thursday's action, which was joined by members of the United Services Union (ver.di) in Germany.

In the US, the Teamsters union said thousands of Amazon workers were involved.

Overall, the group claims to represent "nearly 10,000" Amazon workers, after signing up thousands of people at about 10 locations across the country, many of them in the last few months.

The organisation has demanded recognition from Amazon, accusing the company of illegally ignoring its duty to negotiate collectively over pay and working conditions.

"They've pushed workers to the limit and now they're paying the price. This strike is on them," said the union's general president, Sean O'Brien.

"If your package is delayed during the holidays, you can blame Amazon's insatiable greed."

The Teamsters is a storied US union, with more than one million members overall. It is known for winning robust contracts for members at firms such as delivery giant UPS.

Most of the Teamsters' Amazon campaigns have involved drivers technically employed by third-party delivery firms that work with the tech giant.

Amazon denies that it is on the hook as an employer in those cases, a question that is currently the subject of legal dispute. Labour officials have preliminarily sided with the union on the issue in at least one instance.

Amazon employees at a major warehouse in Staten Island in New York have also agreed to affiliate with the Teamsters.

Their warehouse holds the distinction as the only Amazon location in the US where a union victory has been formally ratified by labour officials.

But it has seen little progress when it comes to contract negotiations since the 2022 vote. It was not among the locations listed to go on strike on Thursday.

Amazon, one of the largest employers in the US, has long faced criticism of its working conditions and been the target of activists hoping to make inroads among its workers.

Its fierce opposition to unionisation efforts has also been called into question.

But it is not the only business facing pressure over its refusal to come to the table about a contract years after the start of unionisation efforts.

At Starbucks, where the first coffee shop voted to unionise in 2021, workers also recently authorised a labour strike, accusing the company of dragging its feet on negotiations.