Boys champion Borna Coric (L) of Croatia and girls champion Ana Konjuh of Croatia pose after their matches at the US Open tennis championships in New York, Sept 8, 2013. [Photo/Agencies]

NEW YORK - Croatia made a clean sweep of the junior singles titles at the US Open on Sunday when Borna Coric and Ana Konjuh posted victories at Flushing Meadows.

The fourth-seeded Coric defeated Australia's Thanasi Kokkinakis 3-6 6-3 6-1 in the final of the boy's singles before the second-seeded Konjuh beat American wildcard Tornado Black 3-6 6-4 7-6(6).

Coric, 16, said the US Open would be his last junior tournament.

"I've won the Slam. That was goal at the beginning of the year, so it's an amazing feeling," he said.

Coric has been named to Croatia's Davis Cup team for the tie next week against Britain at Umag.

He admitted his rise to national duty had taken him by surprise.

"It's really unbelievable, I didn't expect it," he said. "Four months ago, if someone told me, I would say no chance.

"But I was working really hard. So I think I deserve it. Whatever the captain says, I'm going to do it. If he says you play, I will play. If he says just bring the water on the court, I will just bring the water on the court."

Konjuh, 15, scored the narrowest of victories after a 75-minute third set. She trailed 3-5 in the deciding tiebreaker.

"I just managed to do it," Konjuh said. "I just want to keep practicing even more to be even better.

"I didn't know until after I finished that Borna also won. We are really good friends. It's not every day that two Croatians win grand slam titles."