The Men of Gwent had been in the hunt for a scrumhalf to replace Danny Lee, who was forced into retirement through injury earlier this season.
And they have now signed Petri from Sale Sharks for the remainder of the season. He will compete with Wayne Evans and youngsters Jonathan Evans, James Leadbeater and Nicky Griffiths for the number nine jersey.
"We will introduce Mike as soon as possible," said Dragons head coach Paul Turner "Jonathan Evans is one for the future and with James Leadbeater and Nicky Griffiths we're back to our five scrum halves which tends to look after the Dragons and the Newport club."
Petri appeared off the bench for Newport RFC, against Glamorgan Wanderers in the Principality Premiership last weekend and has been named in the Dragons' squad to face Connacht on Thursday.
Twenty-Six-year-old Petri made his USA debut in the 2007 World Cup, playing against eventual winners South Africa. He has gone on to win 17 caps and captained his country against Wales in 2009.
Petri was pleased to link up with the Dragons and looks forward to tasting Magners League action.
"I'm delighted to be here, it's a great opportunity and I'm looking forward to getting on the pitch for the Dragons," he added.
63x46.png){kind=logo}