Donald Trump's top domestic security official urged voters Tuesday to be patient in waiting for election results after reports that the president could rush to claim victory.
"Voters should be patient while waiting for the outcome of this year's election," said Chad Wolf, the acting secretary of homeland security.
"It is important to recognize that this process may require time."
Trump reportedly told confidants that he would declare victory late Tuesday if it looked like he was ahead in the voting, though he denied the accusation.
As voting opened, he told Fox News that there was "no reason to play games" over declaring victory early.
Officials in many states have said that counting the large numbers of mail-in votes could take at least another day, and perhaps three days.
Wolf told a press briefing that US election systems remain "resilient" despite attempts by foreign countries like Iran and Russia to hack them and to obtain voter data.
"We have no indications that a foreign actor has succeeded in compromising or affecting the actual votes cast in this election. But we do remain on high alert," said Wolf.
Chris Krebs, the head of the Cybersecurity and Infrastructure Security Agency, which is in charge of election security, said he is confident that the vote results, which will only begin coming in on Tuesday evening, will be secure.
But he warned that there was still time for people to try and disrupt the election, or for breakdowns in voting technology.
"There may be other events or activities or efforts to interfere and undermine confidence in the election," Krebs said.
"So I ask all Americans to be patient, to treat all sensational and unverified claims with skepticism," he said.