May and Juncker have only been in touch by text message since Tuesday, when the British parliament rejected their Brexit divorce deal.
“President Juncker will talk to Prime Minister May today early afternoon at her request,” European Commission Spokesman Margaritis Schinas said.
“I don’t know how decisive or not this will be.”
British politicians are now wrangling over how to get out of the impasse, which could see Britain crash out of the union without a deal on March 29.
EU leaders have so far ruled out renegotiating the agreement, but have signalled they could postpone the withdrawal if May comes up with a plan.