Malik is allegedly attempting to save his relationship with the Little Mix singer after Australian waitress Courtney Webb claimed in the press that she slept with him last week.
[Left: Justin Bieber / Right: Zayn Malik and Perrie Edwards]
Bieber has now pledged allegiance to Malik and offered to take him on a trip to Las Vegas if he needs cheering up, commenting: "That is what buddies do."
"I am there for him whatever he is going through - that is what buddies do," he told Yahoo OMG.
"If he wants to go away and have a little trip to get away from things that is cool. We could go and do a weekend in Vegas and just get away from everything.
"All the One Direction guys are my buddies - but I do get along really great with Zayn... He is a really good guy."
Bieber, who recently split with his girlfriend Selena Gomez, also stressed how "tough" it is to have personal issues played out in public.
[Justin Bieber with One Direction stars Zayn Malik and Niall Horan]
"We are blessed to be doing what we are doing - but I know how tough it can be dealing with something that should be private in the public eye," he said.
"All you want is privacy but you know it isn't going to happen."
Malik's lover has allegedly been taken into hiding after One Direction fans sent her death threats and located her London home.
A friend of the popstar posted Webb's phone number on Twitter yesterday (January 29), resulting in her receiving "hundreds of calls from all over the world".
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