The SEC, under its existing authority to require full disclosure, has declared that investments in countries under US sanctions are a significant material risk to investors.

CENTERFORSECURITYPOLICY: Center For Security Policy

"The pressure on the US rating is increasing, " said Fitch's David Riley, adding that if there was no deal, there was a "material risk" of a downgrade.

BBC: Triple A letters

The SEC, he said, has often updated its assessment of what constitutes material risk for investors, beginning with new environmental criteria following the Love Canal toxic dump scandal of the late 1970s.

CENTERFORSECURITYPOLICY: Center for Security Policy | Their Finest Hour��: Financial Times Describes Emerging Forces in Global Finance and National Security/Human Rights Nexus