Sullivan, whose last cap was in February 2003, joined United on a free transfer from Chelsea in the summer and has been in splendid form all season, even allowing Scott Carson to leave recently.
Sullivan is expected to play through the pain barrier tomorrow after requiring an injection ahead of Wednesday's 2-0 defeat at Derby for a finger ligament injury.
Scotland squad for training in Manchester between February 6-9:
Douglas (Celtic), Gordon (Hearts), Marshall (Celtic), Sullivan (Leeds), Anderson (Aberdeen), Caldwell (Hibernian), McNamara (Celtic), McNamee (Livingston), Naysmith (Everton), Pressley (Hearts), Webster (Hearts), Weir (Everton), Dailly (West Ham), Ferguson (Blackburn), Fletcher (Man Utd), Hartley (Hearts), McCann (Southampton), Quashie (Southampton), Crawford (Dundee), Dickov (Blackburn), McFadden (Everton), Miller (Wolves), O'Connor (Hibernian), Riordan (Hibernian), Thompson (Rangers).