Britain's Emma Raducanu has been beaten 6-4 6-3 by Russia's Anna Kalinskaya in the semi-finals of the Washington Open.
The 22-year-old, whose run in the United States has ensured she will regain her British number one spot from Katie Boulter, served five aces early on, but could not convert any of her four break point opportunities.
Kalinskaya, ranked two places below Raducanu at 48th in the world, capitalised with a break in the ninth game on her way to clinching the first set.
The two exchanged early breaks in the second set before the 26-year-old Russian pulled ahead once more, taking a lead that proved decisive and breaking again to seal the win.