BERLIN (Reuters) - German sportswear brand Puma nudged up its sales and profit guidance for 2018 after posting a 12 percent jump in first-quarter revenue but cautioned volatile currencies and the threat of a U.S.-China trade war had tempered its optimism.

Excluding the impact of currencies, Puma now expects sales to increase between 10 and 12 percent in 2018, up from a previous target for a 10 percent rise, it said on Thursday.

It forecasts operating profit in the range of 310 million to 330 million euros ($382-$407 million), compared with previous guidance for 305 to 325 million euros.

"The first quarter saw a strong increase in sales and profitability, but several uncertainties in our business environment have recently developed," Puma said, citing adverse currency developments, political instability and a uncertain trade environment between China and the United States.

($1 = 0.8107 euros)

(Reporting by Caroline Copley; Editing by Maria Sheahan)