Justin Bieber and Mariah Yeater
Kevin Winter/NBCUniversal/Getty; Pacific Coast News
is set to take the next step – a DNA test – to prove he isn't the father of Mariah Yeater's baby
Bieber, 17, has already vigorously denied the 20-year-old fan's claim that he got her pregnant, saying he never even met her.
He will take the test once he returns to the U.S. from Europe next week, a source tells PEOPLE.
The pop superstar is also likely to sue Yeater and the people representing her to show there are consequences to making false accusations.
"It's disappointing that people would stoop so low, but somebody needs to stand up to them," says the source.
Yeater is seeking financial support from Bieber. A rep for Bieber told PEOPLE in a statement: "It's sad that someone would fabricate malicious, defamatory, and demonstrably false claims. We'll vigorously pursue all available legal remedies to protect Justin and to hold those involved with bringing this suit accountable for their actions."
Bieber performed Sunday at the MTV Europe Music Awards
in Belfast, Northern Ireland, a show hosted by his girlfriend, Selena Gomez
. He won two awards, including best male act.
TMZ first reported the DNA-test story.
With reporting by JOEY BARTOLOMEO