'Buy With Prime', which was launched as an invite-only offering in April, will be widely available to U.S.-based merchants by Jan. 31, the company said. It added that the product has increased shopper conversion rate by an average of 25%, meaning that many more people placed an order when 'Buy with Prime' was available versus when it was not.Prime members, who pay $139 per year and drive most of Amazon's sales volume, can buy products from these merchants by clicking the 'Buy With Prime' button on their storefront.The offering competes with the Shopify Pay feature offered by the Canadian company, which has emerged as an alternative for online merchants looking to directly sell products to consumers.Several Amazon merchants, mostly small and medium-sized, started selling products directly to customers via their websites during the pandemic, citing high shipping costs and limited warehouse capacity.CNBC had reported in September that Shopify was warning merchants trying to install 'Buy With Prime' button that the feature violates its terms of service. (Reporting by Yuvraj Malik in Bengaluru; Editing by Shailesh Kuber)