WASHINGTON (NEXSTAR) - TikTok's lawyers say the app could go dark in the U.S. as early as Sunday. Congress set that deadline for TikTok to find a new owner or get off the app store. Lawyers for TikTok say that's effectively a ban. A Biden administration official says because this deadline is over the weekend they're not going to enforce the law, it'll be up to the Trump administration. “TikTok must not go dark on Sunday,” said Sen. Ed Markey (D-Mass.). Congress set a Sunday deadline for the Chinese parent company that owns TikTok to either divest or face a ban in the U.S. The bipartisan move senators say was based on national security concerns. “We are against a Chinese company that is in cahoots with the Chinese Communist Party owning TikTok,” said Sen. Chuck Schumer (D-N.Y.). A close advisor to President-elect Donald Trump says he's looking for ways to preserve TikTok. Trump used the app during the campaign and TikTok’s CEO is expected to attend President-elect Trump's inauguration. “There is no reason why TikTok has to go dark in three days,” said Markey. A group of Senate Democrats wrote a letter to President Joe Biden asking him to extend the deadline and at the Supreme Court TikTok argued a ban would violate the First Amendment. They're awaiting a ruling. Some lawmakers say TikTok’s parent company has run out of time. “TikTok's owners had plenty of time to find a buyer,” said Sen. Tom Cotton (R-Ark.). The Supreme Court announced Friday morning they will uphold the ban.