WEST PALM BEACH, FLA. -- U.S. President Donald Trump complained Saturday about House Speaker Nancy Pelosi's delayed transmission of the articles of impeachment to the Senate, which may delay a trial in the GOP-controlled chamber.

"It's so unfair," Trump said, days after he was impeached by the House, as he spoke at a conservative student conference organized by the group Turning Point USA. "They are violating the Constitution," he added.

Pelosi has refused so far to send the articles of impeachment to the Senate, in part to provide more leverage to Democrats in that chamber as they seek to negotiate the rules for the trial proceedings. Senate Majority Leader Mitch McConnell and Democratic leader Chuck Schumer remain at an impasse over whether there will be new witnesses and testimony in the trial.

Still, Trump is expected to be acquitted of both charges in the Senate, where Republicans have the majority, in what will be only the third presidential impeachment trial in U.S. history. Proceedings are expected to begin in January.

Trump lashed out at the Democrats who supported impeachment, accusing them of trying to "overthrow" the 2016 election.

"They call themselves Democrats, but they really don't believe in democracy," he said.

Trump lauded House Republicans for remaining in lockstep against impeachment as a few Democrats crossed the aisle to oppose it.

"We have to say it was a bipartisan vote," Trump said. "No Republican went to their side."

Speaking to thousands of enthusiastic supporters, many wearing his campaign paraphernalia, Trump encouraged young conservatives to stand up to the "radical left," as he sought to harness the nation's cultural and divisions for political gain.

"The Democrat Party is trying to shred our Constitution, tear down our history and erase the nation's borders," Trump said.

"Each of you are on the front lines of defending our way of life," he added. "The radical left doesn't stand a chance against young conservatives who put America first."

Trump spoke on the first day of his more than two-week winter vacation at his private club in Palm Beach.

Trump was introduced by conservative talk radio host Rush Limbaugh, who encouraged the high school students in attendance not to believe in climate change and for conservatives to attack Trump's critics, not spend time defending him.

"The people that need to be defending themselves are the people attacking him and the people attacking us," Limbaugh said. "The president doesn't need to be defended. He needs to be supported."