United scored four times in the first 26 minutes yet despite never leading by less than two goals, seldom looked secure once the Red Bulls got their attack in gear.
Red Bulls coach Juan Carlos Osorio fielded a strong squad yet his choices couldn't contain a D.C. team missing starters Ben Olsen, Dejan Jakovic, Jaime Moreno and Clyde Simms. Pontius nailed home a Christian Gomez corner kick in the eighth minute and 10 minutes later Gomez played Boyzzz Khumalo into space behind the New York back line for a clean chance he steered past goalie Danny Cepero.
Three minutes later, it was 3-0. Cepero saved a shot from Ange N'Silu but in doing so banged the ball into the path of Brandon Barklage, who knocked it in. Fred did the honors in the 26th minute by racing through to test Cepero; his lunge blocked the ball into the chest of Fred, who ran the ball into the net.
New York finally mustered up a few shots, and after United keeper Josh Wicks repelled a bending shot by Khano Smith late in the first half, Dane Richards got the Red Bulls on the board by running onto a ball from John Wolyniec and drilling a shot past Wicks in the 44th minute.
For the second half Osorio sent out Jorge Rojas, who is under league suspension for elbowing Houston's Brian Mullan in a match last Saturday but is eligible for U.S. Open Cup competition. Three minutes into the second half he connected with a deflected cross to pound a shot past Wicks. Score: 4-2. Anxiety amongst D.C. fans, much more familiar with their team doing the rally thing: rising.
A bit of Keystone Kops defending enabled United to restore the three-goal lead in the 52nd minute. Cepero came out to punch a cross from Fred but couldn't reach it. Instead, he stumbled over teammate Kevin Goldthwaite as Pontius nodded the ball into the net.
Defender Greg Janicki handled a ball in the penalty area near the hour mark, and Rojas converted to tighten the D.C. nerves once again.
But a few more New York chances went unexploited, with Wicks diving at the feet of Danleigh Borman to push the ball to safety in the final minutes, and United prevailed to move into the Open Cup third round (final 16) as one of eight MLS representatives. It will play an opponent to be determined next month once qualifying rounds are completed.
U.S. Open Cup
May 20 in Washington, D.C
D.C. United 5, New York 3
Goals: Pontius (Gomez) 8, Khumalo (Gomez 18), Barklage 21, Fred (Pontius) 26, Pontius (Fred) 52; Richards (Wolyniec ) 44, Rojas (Wolyniec ) 48, Rojas (penalty kick) 61.
D.C. United -- Wicks, Namoff (DiRaimondo 67), Janicki, McTavish, John, Barklage, Gomez (Jacobson ,46), Fred (Wallace 58), Khumalo, N'Silu, Pontius (Burch 80).
New York -- Cepero, Hall, Boyens (Zimmerman ,46), Mendes, Borman (Ubiparipovic 83), Richards, Pietravallo (Rojas 46), Sassano, Smith (Goldthwaite 46), Oduro, Wolyniec.
Referee: Mark Kadlecik