WASHINGTON, July 21 (Reuters) - The U.S. Securities and Exchange Commission is likely to embark on a renewed effort to write "long overdue" rules for the registration and regulation of security-based swap execution facilities, Chair Gary Gensler said on Wednesday. In a prepared speech, Gensler said he wanted the SEC to harmonize such derivatives rules with similar ones already in place at the Commodity Futures Trading Commission. He also emphasized that any crypto token or similar product priced off the value of securities must adhere to securities laws, even when offered on a decentralized platform. "These platforms — whether in the decentralized or centralized finance space — are implicated by the securities laws and must work within our securities regime," he said in a speech to the American Bar Association. On swaps, Gensler"s remarks inject new life into a long-running project at the SEC to apply stricter oversight to the securities portion of the derivatives market, as directed by the 2010 Dodd-Frank financial reform law. The CFTC has the bulk of responsibility for overseeing derivatives, but the SEC has lagged in its efforts to write required rules for the relatively small portion of the securities-based derivatives market. Gensler said he had told SEC staff to harmonize its rules with ones already in place at the CFTC, a process that will likely see the SEC put out a fresh proposed rule for public comment. The SEC first proposed rules for securities-based swap execution facilities in 2011. Gensler said pairing SEC rules with the CFTC regime will be an efficient approach, as many firms affected by new SEC rules already operate under the CFTC regulations.