The rupee strengthened by 4 paise to 65.10 per dollar in opening trade today on some selling of the US currency by exporters and banks. A positive opening for the stock markets also boosted the domestic currency, dealers said. Yesterday, the rupee had lost 25 paise to 65.14 on fresh bouts of demand for the American currency from importers and banks amid rising uncertainty stemming from US President Donald Trump's possible trade war.