GREENSBORO, N.C. (AP) - No. 4 North Carolina, appearing tired and beaten for 40 minutes, dug down deep in overtime, scoring on its first nine possessions of the extra period Saturday to beat No. 21 Maryland 83-73 in the ACC tournament semifinals.

Shammond Williams scored 10 of his 25 points in the overtime to lead the Tar Heels (29-3) to the Atlantic Coast Conference finals for the seventh time in the 1990s.

North Carolina has now beaten the No. 3 seeded Terrapins (19-10) for the sixth straight time in the ACC postseason and denied Maryland its first trip to the title game since 1984.

Williams made 2-of-3 free throws with four seconds left in regulation to tie the score at 66-66, then took over in overtime, scoring on a fastbreak layup, a shot in the lane, a 19-footer and four free throws.

Ademola Okulaja also added a key 3-pointer in the extra period as the Tar Heels scored on every possession except the final one, when they ran out the clock after outscoring Maryland 17-7 in the extra period.

Vince Carter added 18 points and Antawn Jamison 15 as North Carolina pushed its ACC tourney semifinal winning streak to 11 straight dating to 1984.

Rodney Elliott paced Maryland with 16 points and 10 rebounds.

North Carolina, which lost to Maryland in overtime earlier in the season, was forced to its thin bench early in the second half when starting center Makhtar Ndiaye fouled out with 15:48 remaining and was replaced by freshman Brendan Haywood, who finished with six points, four rebounds and a key block in 16 minutes.

The score was tied 41-41 before Sarunas Jasikevicius sparked a Maryland rally, hitting a 3-pointer, a follow shot and a driving shot in the lane as the Terrapins went up 53-44 with 9:42 left and had most of the partisan North Carolina crowd sitting on its hands.

But the Tar Heels, looking like a weary team that was outhustled to loose balls all day, made one last push. A 16-6 run capped by a Jamison layup gave North Carolina a 60-59 lead with 3:36 left, setting the stage for a furious finish.

After three lead changes, Laron Profit fouled Williams from 3-point range with four seconds left. The 90 percent free-throw shooter made his first two foul shots. Then Maryland called a 20-second time out and a conference with the officials over a Terrapin substitution left Williams standing around for several minutes.

His third attempt was short, Maryland's inbounds pass was picked off by Jamison at halfcourt and his desperation shot was off the mark, sending the game into the extra period.