The CDU/CSU conservative parliamentary bloc has been wrangling for weeks over how strict security requirements for the rollout should be, and whether they should effectively shut out Chinese technology giant Huawei [HWT.UL] from the network.
Merkel favours strict security requirements for the 5G network, but opposes excluding individual companies. She has asked her conservative lawmakers to wait until after a March EU summit before taking a position on whether Huawei can take part.
Norbert Roettgen, the head of parliament's foreign affairs committee, favoured taking a stance before then and said a growing number of lawmakers from the CDU/CSU 'Union' backed a trustworthiness test of firms bidding to join the 5G rollout.
"In the end, it must be clear that in addition to technical verification, there is also a political assessment of the trustworthiness of network equipment suppliers such as the Chinese group Huawei," he said.
"Only companies that are not at the mercy of their home country can be trustworthy," he added. "There are already 50 to 60 members of the Union who want such a trustworthiness test."
Merkel's junior coalition partners, the Social Democrats, have backed their own internal proposal that, if adopted by the government, could effectively translate into shutting out Huawei.
The groundswell of support in the CDU/CSU bloc for a tough line on Huawei means a softer stance could struggle to find a majority in parliament. Roettgen believed the government would come around to supporting a credibility test too.
Take-up of 5G technology is expected to be on the agenda at the March EU summit. Roettgen wants the CDU/CSU parliamentary group to take a stance on Feb. 11 once the European Commission has issued its view at the end of this month.
The United States says gear provided by Huawei, the leading telecoms equipment vendor with a global market share of 28%, contains "back doors" that would enable China to spy on other countries.
Shenzhen-based Huawei has denied allegations by the Trump administration, which imposed export controls on Huawei in May, hobbling its smartphone business and raising questions over whether the Chinese company can maintain its market lead.
(Writing by Paul Carrel; Editing by Alexandra Hudson)
By Andreas Rinke