American teenager Coco Gauff slammed US Open officiating after battling to a stormy first round victory over German veteran Laura Siegemund on Monday.

The 19-year-old American sixth seed – tipped by many as one of the favourites for the this year's title – was forced to dig deep before winning 3-6, 6-2, 6-4 in 2hr 50min on the Arthur Ashe Stadium.

But an ill-tempered clash was marked by angry confrontations by both players with chair umpire Marijana Veljovic.

Gauff remonstrated with Veljovic at length during the third set, accusing the Serbian official of failing to properly enforce time violation rules against Siegemund.

Siegemund – who was warned twice for slow play, eventually costing her a game in the final set – also confronted Veljovic during a tetchy encounter.

Gauff later said she had snapped in frustration at Veljovic's perceived failure to crack down on Siegemund's pace of play.

"I felt like the rules were being bent," Gauff said. "That's why a lot of players get mad when these time violations are called because one ref is letting them go over, the other is more strict on the time.

"I think tennis needs to be more strict on the rules for everybody regardless of every situation."

Gauff said she eventually approached the umpire after she "reached a point where I was just really frustrated."

"I try my best not to let my emotions to take over myself," she said. "When it happens over and over, I'm not going to complain if it's once or twice. It was at least seven times that I counted."

'RESPECTLESS' FANS

Siegemund, 35, meanwhile slammed the partisan home crowd on Arthur Ashe that had cheered her every error relentlessly throughout.

"I am very very disappointed of the way the people treated me today," she told reporters.

"I'm a fighter. I never did anything against the audience, I stayed calm, not even a gesture against the audience. They had no respect for me, no respect for the way I played, no respect for the player that I am, they had no respect for good tennis."

Siegemund admitted she plays slowly but denied it was a tactic to unsettle her opponent.

"There's no doubt about it that I'm slow," she said. "There's no doubt about it that I have to be quicker. But it's how I play. But I do it for me, I don't do it against the (opponent)."

Siegemund fought back tears as she admitted the crowd reaction would make her think twice about playing the tournament in future.

"This kind of unfair, respectless behaviour towards the non-American player. I have only experienced it here on this court," she said.

"I won here two times. I left every minute of every game I played here, everything left out on the court. And this is how (they) treat me? To be treated like that? I will only come back because it's a Slam. For sure not because of the people and to give them a show."

Gauff will face a second round duel with 16-year-old Russian Mirra Andreeva.