** Shares of buy now, pay later firms rise premarket after U.S. President Donald Trump calls for one-year cap on credit card interest rates at 10%, starting January 20
** Investors say the proposal can push borrowers away from traditional credit cards and toward alternative lenders, including BNPL providers
** However, some analysts say imposing a cap on interest rates will require legislation and can exceed the president's authority
** Klarna KLAR.N rises 6.5%, while Affirm AFRM.O up 4%
** Afterpay-owner Block XYZ.N gains 2.4% and Sezzle SEZL.O up 4.3%
(Reporting by Pritam Biswas in Bengaluru)
((Pritam.Biswas@thomsonreuters.com))