Cisco Systems’ CEO John Chambers has written to U.S. President Barack Obama, asking for his intervention so that U.S. technology sales are not affected by a loss in trust as a result of reports of surveillance by the U.S. National Security Agency. The letter follows reports that even as the U.S. warned customers that Chinese networking equipment may be used to spy on them, the NSA physically intercepted routers, servers and other network equipment to plant surveillance tools before repackaging the devices with a factory seal and sending the products to international customers.

Warning of an erosion of confidence in the products of the U.S. technology industry, John Chambers, the CEO of networking giant Cisco Systems, has asked President Obama to intervene to curtail the surveillance activities of the National Security Agency. In a letter dated May 15 (obtained by Re/code and reprinted in full below), Chambers asked Obama to create “new standards of conduct” regarding how the NSA carries out its spying operations around the world. The letter was first reported by The Financial Times. The letter follows new revelations, including photos, published in a book based on documents leaked by former NSA contractor Edward Snowden alleging that the NSA intercepted equipment from Cisco and other manufacturers and loaded them with surveillance software. The photos, which have not been independently verified, appear to show NSA technicians working with Cisco equipment. Cisco is not said to have cooperated in the NSA’s efforts.