Greece wants its EU peers to pledge to keep their borders open to refugees until March or it will refuse to adopt an accord keeping Britain in the bloc at marathon talks on Friday, a government source said.

"We are asking for a unanimous decision that until (an EU-Turkey summit planned for) March 6, no state will unilaterally close its borders... if not, the Greek government will not approve the conclusion text" at the so-called Brexit summit, the source told AFP.