The statement was made in an interview that will air on Sunday on the American broadcaster NBC.
Iran has repeatedly demanded that frozen Iranian assets be returned if an agreement is to be reached.
"That will come later. If they (Iran) behave, if they do a good job, then we can start talking." Trump said in the interview, which was conducted on Friday on the influential program Meet the Press.
Iran's propaganda that sanctions must be lifted before an agreement is also not relevant, according to Trump.
He also claimed that he knows where Iran stores enriched uranium.
"We'll take it out (of the country) and destroy it (in a deal)." Trump said.
