Republican lawmakers are seeking to punish Libya over its failure to bring anyone to justice for the 2012 attack against the US mission in Benghazi.

Congress approved a spending bill earlier this year that ties US aid to the country on progress in the investigation. And House Republicans are threatening to undermine the Obama administration's bid to eliminate Cold War-era visa restrictions that the State and Defense departments have been pushing for since before the fall of Moammar Gadhafi.

The visa restrictions date from 1983 and prohibit Libyans from coming to the United States to engage in flight training, aviation maintenance or nuclear-related studies. The Obama administration argues that the restrictions have strained relations with a potential partner in a strategically vital part of the world — and put a $2 billion training program at risk.

The argument for better relations has failed to impress Republicans as they ramp up their criticism of the Obama administration's response to the attack that killed Ambassador Christopher Stevens and three other Americans ahead of the 2014 midterms.