According to a Nikkei report on Friday, Apple has asked suppliers to make sure that shipments from Taiwan to China comply with the latter’s customs laws to prevent them from being held for inspection.

Following the visit to Taiwan by Speaker of the US House of Representatives Nancy Pelosi and a congressional delegation, trade tensions between the US and China have risen.

The report claimed, citing sources familiar with the situation, that the iPhone maker informed suppliers that China has begun enforcing a long-standing requirement that Taiwanese-manufactured parts and components must be identified as made either in “Taiwan, China” or “Chinese Taipei.”

In response to a media report that claimed shipments to Pegatron’s facility in China were being held for inspection by Chinese customs officials, the Apple iPhone assembler Pegatron confirmed its mainland China plant is operating regularly.

Foxconn and Pegatron, two Taiwanese suppliers and assembly companies, are stepping up their production efforts as Apple prepares to introduce the new iPhone in September.