Manchester United have all but rubber-stamped their first signing of the summer.
Swansea are reportedly set to collect an initial £15 million for the Welsh international. The fee could rise by £3 million in performance-related add-ons.
"I know the United fans will get behind him and enjoy watching him," Wales manager Ryan Giggs, who handed James his first international cap, told the Guardian. "It's fantastic for everyone, I think. For Dan, for Manchester United, and it's a good deal for Swansea as well. It's the biggest club in the world so my message to him is, enjoy the challenge. Don't be anyone else, and you'll be fine."
James left Wales' camp ahead of Saturday's Euro qualifier against Croatia to finalize the transfer.
"You don't want things weighing on players' minds so if you can get it sorted, it's better for us and the player as well," Giggs added.
United reportedly put the deal on hold after James' father died suddenly at the end of May.
The 20-year-old is coming off a breakout season with Swansea in the Championship, where his pace and trickery on the left flank torched defenders. He recorded four goals and seven assists in his first full season of English football.