Dallas will link up with Northern Ireland after United’s Championship game at Derby County on Saturday, a match which signals the start of the Championship’s first international break.
Michael O’Neill’s side play the Faroe Islands next Friday before travelling to Hungary the following week.
Northern Ireland are in firm contention to qualify automatically for the European Championship finals and are second in their group after six matches, one point behind leaders Romania.
Dallas, who Leeds signed for £1.3m from Brentford three weeks ago, is in line to win a sixth full cap.
The 24-year-old has made an encouraging start to his career at Elland Road and he set up Chris Wood’s equaliser in a 1-1 draw at home to Sheffield Wednesday on Saturday.
Wolves, meanwhile, have rejected a third offer from Norwich for striker Benik Afobe.
A club statement read: “Wolves can confirm that a third bid from Norwich City for Benik Afobe has been immediately rejected.
“The club’s position, outlined on Wednesday, August 19, 2015 remains unchanged.”
Wolves are determined to keep the 22-year-old who scored 32 goals last season after arriving from Arsenal for around £2million in January.
He netted 13 times for Wolves following his move from the Gunners after scoring 19 on loan at MK Dons in the first half of last season.
Afobe was left out of Tuesday’s 2-1 Capital One Cup win over Barnet and afterwards boss Kenny Jackett insisted the forward was going nowhere before the transfer deadline.
He said: “There is an enormous amount of speculation but he won’t be leaving. There are big things at stake and it is not just about one player.”