"I ran as a proud Democrat. I will now be an American president. I will work as hard for those who didn't vote for me - as those who did," said Biden.

Trump signaled on Saturday that he would not accept Biden's victory and vowed to mount legal challenges in court.

WASHINGTON, Nov. 8 (Xinhua) -- Democrat Joe Biden declared victory for the U.S. presidential election on Saturday night, days after Election Day, since races in several battleground states were too close to call with a record number of mail-in ballots to be counted.

President Donald Trump hasn't conceded defeat but vowed to take what he believes are election misconduct to the court, thrusting more uncertainty upon an already exhausted and divided country.

URGING UNITY AMID DEEPENING DIVISION

Speaking from Wilmington, Delaware, Biden touted a "clear" and "convincing" victory while repeating a message of unity after a politically polarized election.

"I ran as a proud Democrat. I will now be an American president. I will work as hard for those who didn't vote for me - as those who did," he said.

Trump signaled on Saturday that he would not accept Biden's victory and vowed to mount legal challenges in court.

Biden's remarks came multiple hours after major U.S. media networks called the presidential race in favor of him after he was projected to take Pennsylvania, a key "battleground state" carrying 20 electoral votes.

In addition to Pennsylvania, Biden was forecast to win back Midwestern states of Wisconsin and Michigan, which have 26 electoral votes together. These three states, once dubbed as the "blue wall," all went to Trump's column in 2016.

For Trump, he held onto Florida and Ohio. The races in Georgia and North Carolina have not been called.

Meanwhile, Democrats are expected to keep control of the House but their majority is expected to be narrower. In the Senate races, Republicans and Democrats are deadlocked at 48 seats each for now.

Crowds of people gathered in Washington, D.C., Austin and other cities to celebrate Biden's projected victory.

Speaking to Xinhua near the White House, local resident Charlie Passut said he doesn't know how much Biden will be able to get done if Congress is divided, adding that the Democrat will "have a lot of work to do."

As of Saturday evening, Biden has received nearly 75 million votes nationwide, while Trump has garnered more than 70 million, according to Fox News. Both have broken Barack Obama's record for popular vote set in 2008.

"The election revealed the U.S. is now one country but two nations," tweeted Richard Haass, president of the Council on Foreign Relations, a U.S. think tank. "We have sorted ourselves into communities & regions with those of similar views. They will have to coexist; whether they can work together remains to be seen."

LEGAL CHALLENGES

"This election is far from over," Trump said in a statement earlier in the day, adding that starting Monday, "our campaign will start prosecuting our cases in court."

The Trump campaign has already launched multiple lawsuits in several battleground states, including Pennsylvania, Michigan, and Georgia.

The campaign has also called for a recount in Wisconsin, while a state official in Georgia has said there would be a recount in the "Peach State" due to a small margin.

Supporters of the president gathered in places across the United States on Saturday, insisting that the election hasn't finished.

Hundreds of Trump's supporters gathered at the Arizona Capitol on Saturday afternoon, protesting that the presidential race was called for Biden.

Trump has previously suggested that he may take the cases to the U.S. Supreme Court, where conservatives have a solid 6-3 majority, including three justices nominated by him.

In 2000, the country's highest federal court decided in a disputed recount of votes in Florida with a 5-4 ruling, effectively handing that year's presidential election to the Republican presidential candidate and then-governor of Texas George W. Bush, who won 271 electoral votes, one more than a majority.

Christopher Galdieri, a political science professor at Saint Anselm College in northeastern state of New Hampshire, told Xinhua that unlike the 2000 Florida case "there are no clearly litigable questions" this year.

"The Trump strategy seems to be to file lots of lawsuits," Galdieri said. "This is very much a long-shot strategy and I am skeptical that it will work for them."

Besides, election disputes would have to go through lower courts before they could reach the high court, according to other U.S. election and legal experts.

A federal law sets what is called the "Safe Harbor" deadline, falling on Dec. 8 this year, the day by which states must submit the winner of the presidential election if they are to be insulated from legal disputes.

Electoral College representatives will meet six days later, on Dec. 14, to formally select the next U.S. president. The U.S. Congress will meet in joint session to count the electoral votes on Jan. 6 next year. The Inauguration Day is Jan. 20.

DAUNTING CHALLENGES

Biden has made the ongoing COVID-19 pandemic a central issue of his presidential bid and put Trump on the defense in their debates over the public health crisis, which has infected more than 9.8 million people in the United States, with nearly 237,000 deaths.

The country set a new record on Friday when the number of its daily cases reached more than 125,000.

Biden said Saturday night that he will name a group of scientists and experts as "transition advisors" to convert his plan to respond to the pandemic into an action blueprint.

"We cannot repair the economy, restore our vitality, or relish life's most precious moments ... until we get this virus under control," he said.

"Everything hinges on his administration's efforts to control the pandemic," Clay Ramsay, a researcher at the Center for International and Security Studies at the University of Maryland, told Xinhua.

According to The Washington Post, Biden is also planning to quickly sign a series of executive orders after taking office to rejoin the Paris Climate Accord, return to the World Health Organization, revoke a ban on immigration from some Muslim-majority countries, and allow "Dreamers," brought to the United States illegally as children, to remain in the country.