Alexander Zverev retained his Citi Open title with a straight-sets victory over teenager Alex de Minaur.

Top seed Zverev claimed his third Tour-level trophy of the season and the ninth of his career with a 6-2 6-4 win on a hot Sunday in Washington.

The world number three did not face a single break point, winning 90 per cent of points on his first serve to deny 19-year-old Australian De Minaur a dream triumph in his maiden ATP World Tour 500-level final.

Zverev got off to a flying start, breaking twice in the first set and once in the second to come out on top.

He took a firm grip on the final by winning the opening four games and lost just five points behind his strong serve in the first set.

Rising star De Minaur was up against it when he went a break down at 2-1 in the second, but showed his fighting spirit by saving three break points before holding to deny Zverev a 5-3 lead.

De Minaur saved four match points in a semi-final win over Andrey Rublev and fended off another three in the showpiece before the tiring youngster crashed a backhand into the net to give Zverev the title.