In a closed-door meeting, Kirstjen Nielsen, the homeland security chief, also vowed retaliation against nations that interfere in the midterm elections this year.
The New York Times obtained a list of people who attended, including ambassadors from across the world. A Department of Homeland Security spokesman confirmed the speech at Blair House but declined to provide details.
Ms. Nielsen’s speech came a week after Mr. Trump said “it certainly looks like the Russians were behind” a nerve-gas attack in Salisbury, England, that poisoned a former Russian spy and his daughter. Two dozen countries, including the United States, have since expelled Russian officials in a punishing diplomatic purge.
But otherwise, Mr. Trump has mocked the notion of election meddling by Moscow, at times calling it a “hoax,” concocted by Democrats and Hillary Clinton, his opponent in the race, after they lost. American intelligence agencies, however, have concluded that Russia did interfere in 2016 and intends to continue during midterm elections in November.
The Department of Homeland Security is working with state and local election officials to protect electoral systems from cyberattacks. Congress last week approved spending $380 million for states and localities to step up its online security efforts during the 2018 midterm campaign.
During a Senate hearing last week on election security, Ms. Nielsen said the department was speeding up security clearances to give state and local officials classified threat briefings. So far, about 20 state election officials have received full security clearances while others have received interim clearances.
She also said the department had given in-depth vulnerability assessments of voting systems to 15 of 19 states that so far had requested them. The remaining states will get that assistance before Election Day, Ms. Nielsen said.
One department official, speaking on the condition of anonymity, said Ms. Nielsen’s speech underscored her intent to prevent digital intrusions by foreign nations on critical infrastructure systems such as banks, electric utilities and election systems.
Election systems were designated as critical infrastructure by Jeh Johnson, the former homeland security secretary to President Barack Obama. The designation guarantees that states are given priority assistance when they request help and greater access to information on online vulnerabilities. The federal assistance is voluntary.
United States Politics and Government,Russian Interference in 2016 US Elections and Ties to Trump Associates,Midterm Elections (2018),Cyberwarfare and Defense,United States International Relations,Homeland Security Department,Nielsen Kirstjen,Moscow (Russia)