Washington (CNN) - President Barack Obama has been privately reaching out this week to candidates for the pending Supreme Court vacancy, an administration source told CNN Tuesday.
The source - who is involved in the ongoing selection process - characterized the talks as "conversations," not formal in-person interviews that often are the last step before a nominee is chosen and announced.
White House officials have said they expect the president to pick his nominee by early May. Justice John Paul Stevens announced he would retire shortly after the court's current term ends in late June.
This latest development signals an intensification of the selection process, after officials in the White House counsel's office spent the past few weeks probing the professional and personal records of top contenders. That list will be narrowed in coming days as staffers make their recommendations to Obama.
The president's conversations were conducted over the phone, but the nature and topic of the discussions were not disclosed by the source, to give Obama a measure of privacy and discretion for such an important decision.
It was unclear which names on the White House short list of about 10 people are being given the most serious scrutiny.
Government sources had earlier told CNN three names had an early edge: Solicitor General Elena Kagan and federal appeals judges Diane Wood and Merrick Garland. But officials stress the president in recent days has expanded the list of names he wanted his staff to vet before he makes his decision.
Others being considered include Michigan Gov. Jennifer Granholm, Homeland Security Secretary Janet Napolitano, and Montana-based federal appeals judge Sidney Thomas.
The administration source would not say when Obama will sit down formally with any finalists. The president meets Wednesday with Senate leaders of both parties to discuss the upcoming vacancy.
Kagan, Wood, and Napolitano were interviewed privately at the White House last year, along with then-Judge Sonia Sotomayor, who eventually was chosen to replace now-retired Justice David Souter.