"Similar to Islamist terrorism this breed of terrorism is inspired by hateful, supremacist and intolerant ideology," Nathan Sales, the State Department's counterterrorism coordinator, told a briefing, adding that the 2018 attack by a gunman who killed 11 people at a synagogue in Pittsburgh was an example of the rising trend.
"Make no mistake we will confront all forms of terrorism no matter what ideology inspires it," Sales said.
He added that white supremacist and other racially motivated terror organizations were copying strategies from armed Islamist groups.
"They are in a sense learning from their jihadist predecessors in terms of their ability to raise money and move money, in terms of their ability to radicalize and recruit."
Mass shootings that killed dozens of people this year in the United States have fueled a long-running debate over gun control.
In August, a suspected white nationalist shot dead 22 people at a Walmart store in El Paso, Texas, shortly after posting an anti-Hispanic manifesto online.
U.S. President Donald Trump said after the shooting that Americans “must condemn racism, bigotry and white supremacy” and blamed the internet and violent video games for fostering violence but some Democrats and El Paso residents said Trump's own rhetoric about an immigrant “invasion” had contributed to racial division.
Asked if any neo-Nazi or white supremacist groups inside the United States had been identified as terrorist organizations, Sales said State Department deferred to the FBI and Department of Homeland Security when it comes to combating domestic terrorism threats.
But he added that the State Department was working with technology companies to develop positive narratives against hateful messages and international partners to mobilize action against these networks.