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Huawei has cut more than 600 jobs at its US research unit Futurewei after Washington put the Chinese firm on a trade blacklist.

The telecoms giant said the job cuts were due to "the curtailment of business operations caused by the US".

Washington added Huawei to its "entity list" in May which restricts its ability to trade with US firms.

Tensions between the US and China over trade and Huawei have escalated this year.

Based in California, Futurewei is a research and development subsidiary of Huawei.

In a statement, Huawei said "Futurewei Technologies announces a reduction in force, directly impacting over 600 US positions," effective 22 July.

The company said the job losses followed the "curtailment of its business operations" in the US after Huawei and 68 subsidiaries were placed on the US "entity list".

The US added Huawei to the trade blacklist in May, a move that bans the company from acquiring technology from US firms without government approval.

In July, the US Commerce Secretary Wilbur Ross said the US the Commerce Department would issue licenses to companies seeking to trade with Huawei where there is "no threat to US national security".

Huawei, the world's largest maker of telecoms equipment, has repeatedly denied claims that the use of its products presents security risks.

US-China tensions

Washington's clampdown on Huawei is part of a wider conflict simmering between the US and China.

The two countries have been fighting a trade war for the past year, imposing tariffs on billions of dollars worth of one another's goods.

The US has targeted Huawei with trade restrictions, while also pushing to persuade allies to ban the Chinese company over the potential risks of using its products in next-generation 5G mobile networks.