(Refiling to restore dropped word "son" to headline)

By Sarah N. Lynch, Jeff Mason and Tom Hals

WASHINGTON (Reuters) -U.S. President Joe Biden's son Hunter Biden has agreed to plead guilty to two charges of willfully failing to pay income taxes and to enter into an agreement that could enable him to avoid a conviction on a gun-related charge, according to a court filing on Tuesday.

The federal charges against Hunter Biden resulted from an investigation by David Weiss, the U.S. attorney in the Democratic president's home state of Delaware, who was appointed by Republican then-President Donald Trump.

Hunter Biden, 53, for years has been the focus of unrelenting attacks by Trump and his Republican allies, who have accused him of wrongdoing relating to Ukraine and China, among other matters. The president's son has worked as a lobbyist, lawyer, investment banker and artist, and has publicly detailed his struggles with substance abuse.

According to court filings, Hunter Biden received taxable income in excess of $1.5 million in 2017 and 2018, but he did not pay income tax those years despite owing in excess of $100,000. The two counts are misdemeanors.

His attorney, Christopher Clark, said the government would file a firearm charge against his client that would be subject to a pretrial diversion agreement, an alternative to prosecution that is sometimes used to allow defendants to avoid prison time or a criminal conviction.

"It is my understanding that the five-year investigation into Hunter is resolved," Clark said. "I know Hunter believes it is important to take responsibility for these mistakes he made during a period of turmoil and addiction in his life. He looks forward to continuing his recovery and moving forward."

Hunter Biden disclosed in December 2020 that Weiss's office was investigating his tax affairs. He denied wrongdoing.

He described in a 2021 memoir dealing with substance abuse issues in his life, including crack cocaine use and alcoholism. He was discharged from the U.S. Navy Reserve in 2014 after testing positive for cocaine, sources said at the time.

President Biden has long expressed support and pride in his son for overcoming his addiction.

The White House on Tuesday declined to comment further.

"The President and First Lady love their son and support him as he continues to rebuild his life. We will have no further comment," spokesperson Ian Sams said in a statement.

The Weiss inquiry initially examined potential violations of tax and money laundering laws in foreign business dealings, principally in China, sources told Reuters. The investigation headed by Weiss began as early as 2018, according to U.S. media reports.

A senior Republican congressman, James Comer, in 2022 accused the U.S. Treasury Department of withholding financial "suspicious activity reports" to shield Hunter Biden's business dealings.

Comer, chair of the House of Representatives Oversight Committee, which has been leading House Republicans' investigations into Biden's family, called the plea deal "a slap on the wrist" and said it would not deter his panel's work.

Trump, who was recently indicted on federal criminal charges that he unlawfully kept national-security documents when he left office, also criticized the deal.

"Wow! The corrupt Biden DOJ just cleared up hundreds of years of criminal liability by giving Hunter Biden a mere 'traffic ticket.' Our system is BROKEN!" he said on his social media platform.

President Biden has two surviving children, Hunter Biden and daughter Ashley Biden. His son Beau Biden died in 2015 of cancer and his daughter Naomi Biden died as an infant after a car accident that also killed Joe Biden's first wife.

Hunter Biden appears to be the first child of a sitting president to be indicted, according to Aaron Crawford, who specializes in presidential history at the University of Tennessee.

Crawford said the family of several presidents were ensnared in scandals, including George H.W. Bush's son Neil, who directed a failed savings and loan, and Richard Nixon's brother Don, who was rescued from business failures by wealthy businessman Howard Hughes.

(Reporting by Sarah N. Lynch, Jeff Mason, Trevor Hunnicutt and Susan Heavey in Washington and Tom Hals in Wilmington, Delaware; Additional reporting by Moira Warburton; Editing by Doina Chiacu, Heather Timmons and Jonathan Oatis)