Secretary of State Mike Pompeo has warned US allies against deploying equipment from Chinese telecoms gear manufacturer Huawei on their soil, saying it would make it more difficult for Washington to "partner alongside them".
"We want to make sure we identify (to) them the opportunities and the risks of using that equipment," Pompeo told reporters on Monday during a visit to the Hungarian capital, Budapest.
Hungary is the first stop in Pompeo's trip to central Europe that also includes Slovakia and Poland, part of an effort to make up for a lack of US engagement in the region that opened the door to more Chinese and Russian influence, administration officials said.
Washington is concerned about China's growing presence, in particular the expansion of Huawei Technologies, the world's biggest maker of telecoms equipment, in Hungary and Poland.
The US and its Western allies believe Huawei's gear could be used for espionage, and see its expansion into central Europe as a way to gain a foothold in the EU market.
Huawei denies engaging in intelligence work for any government. It says its technologies serve 70 per cent of Hungarians and that it co-operates with most telecoms providers in Hungary, including state-owned enterprises.
"We have seen this all around the world, it also makes it more difficult for America to be present," Pompeo said.
"If that equipment is co-located where we have important American systems, it makes it more difficult for us to partner alongside them."
Pompeo announced plans for a defence cooperation agreement with Hungary, one of the most enthusiastic European governments about Chinese investment. But he said he had discussed "the dangers of allowing China to gain a bridgehead in Hungary" in talks with Foreign Minister Peter Szijjarto.
Budapest's nationalist government, largely isolated politically in the European Union, hopes to buy mid-range air defence capabilities from the United States.
In Poland, where Pompeo is travelling to on Tuesday, the government is considering banning Huawei from participating in the development of 5G capabilities after arresting a Chinese employee of Huawei and a former Polish security official on spying allegations last month. Both men have denied wrongdoing.
Pompeo's tour includes a conference on the Middle East, hosted by Poland, where Washington hopes to build a coalition against Iran.
He is also expected to voice concerns about energy ties with Moscow, and urge Hungary not to support the TurkStream pipeline, part of the Kremlin's plans to bypass Ukraine, the main transit route for Russian gas to Europe.