WASHINGTON, Jan 28 (Reuters) -

The United States on Monday charged China's Huawei Technologies Co Ltd, its chief financial officer and two affiliates with bank and wire fraud to violate sanctions against Iran in a case that has added to tensions with Beijing.

In a 13-count indictment, the Justice Department said Huawei misled a global bank and U.S. authorities about its relationship with the subsidiaries, Skycom Tech and Huawei Device USA Inc, in order to conduct business in Iran.

In a separate case, the Justice Department also accused Huawei of stealing trade secrets, wire fraud and obstructing justice for allegedly stealing robotic technology from carrier T-Mobile US Inc to test smartphones' durability.

T-Mobile had accused Huawei of stealing the technology, called "Tappy," which mimicked human fingers and was used to test smartphones. Huawei has said that the two companies settled their disputes in 2017.

The charges add to pressure on Huawei, the world's biggest telecommunications equipment maker, from the U.S. government, which is trying to prevent American companies from buying Huawei routers and switches and pressing allies to do the same.