President Obama's Russian "reset" will face another big test Monday, as he and his diplomats meet with their Moscow counterparts in two different cities on two of the trickiest foreign policy challenges of his administration -- Syria and Iran. 

In the Mexican city of Los Cabos, Obama is expected to meet with Russian President Vladimir Putin on the sidelines of the G-20 summit and have the chance to press Putin over the worsening situation in Syria. 

In Moscow the same day, negotiators from the U.S. will join diplomats from Russia and other countries to meet with Iran over its nuclear program. 

Efforts to stanch the violence in Syria and check Iran's nuclear program have hit serious roadblocks in recent weeks, and Russia is considered critical to untangling both messes. 

Yet the minimal progress has drawn renewed criticism of U.S. policy toward Moscow, albeit criticism that falls on the upswing of the presidential campaign season.