ZURICH, Switzerland — Swiss watch exports resumed a losing streak in April, hurt by weakness in the key markets of Hong Kong and the US, raising concern that a recovery will take time.Exports slipped 5.7 percent to 1.53 billion francs ($1.57 billion), the Federation of the Swiss Watch Industry said Tuesday. Shipments have been negative in 21 of the past 22 months.The result dims the outlook for the industry, which had emerged from its longest consecutively monthly slump on record in March. Some watchmakers have signalled the worst may be over, including LVMH watch chief Jean-Claude Biver, who has forecast Swiss watch exports will increase this year, and Swatch Group AG chairwoman Nayla Hayek, who said Tuesday that 2017 is showing "very promising signals." In contrast, Richemont chairman Johann Rupert said May 12 the world has too many timepieces.“In spite of the tougher comparison base in April, low single-digit growth would have been a very good result, while flat would have been OK, so being slightly down is a little disappointing, but not the end of the world,” said John Guy, an analyst at MainFirst Bank AG.The decline was led by Hong Kong and the US, where shipments slid 17 percent and 19 percent, respectively. The recovery is progressing slower than expected, Zuzanna Pusz, an analyst at Berenberg, said in a note, adding she’s cautious on the market.China continued to show growth with a 39 percent increase, while the U.K. recorded a 30 percent advance, the fastest pace since September.Swatch Group AG chief executive officer Nick Hayek said in March that the weak pound is attracting tourists to buy Swiss watches in the UK, as the currency effect makes some models less expensive there.By Corinne Gretler; editors: Eric Pfanner and Thomas Mulier.