The Reuters report said Verizon has sued Vonage, alleging that it infringed its patents related to VoIP.
The trial began last week and is expected to conclude next week in the US District Court for the Eastern District of Virginia, the Reuters report said.
'First and foremost, we are confident we have not infringed on any of Verizon's patents and, in any case, we believe the Verizon patents are invalid,' Vonage CEO Mike Snyder was quoted in a statement as saying.
Snyder added that the company had enough financial reserves to allow it to maintain normal operations regardless of the litigation's outcome.
The lawsuit filed by Verizon in June last year added to Vonage's woes after a weak stock market debut. Investors have been wary of the shares amid growing competition, as cable companies and other Internet firms offer similar services, the Reuters report said.