Former President Barack Obama urged Georgians to vote in upcoming runoff Senate races, saying the outcomes will determine ultimately the course of the Biden presidency.

You are now once again the center of our civic universe, Obama told Georgia residents Friday during a virtual rally for Democratic Senate candidates Rev. Raphael Warnock and Jon Ossoff.

Both candidates are in high-stakes runoff races for seats that will determine which party controls the U.S. Senate for at least the next two years. In the runoff, set for Jan. 5, Warnock and Ossoff are running against Republican incumbent Sens. Kelly Loeffler and David Perdue , respectively.

President-elect Joe Biden and Vice President-elect Kamala Harris will be working with a GOP majority in the Senate unless Democrats win both their races in Georgia.

I know something about the importance of the U.S. Senate, Obama said. When he was in office, Republican lawmakers repeatedly sought to obstruct legislation key to his agenda, including on immigration reform and expanding access to health care.

Obama also said he had been frustrated by many of his own supporters while in office, saying it seemed as if they felt like they didnt need to do anything after the presidential election because we got Barack there.

This is not just about Georgia. This is about America, and this is about the world, he said. And its in your power to have an impact.