By Doina Chiacu

WASHINGTON (Reuters) -U.S. President Joe Biden will no longer speak at gathering of the largest U.S. teacher’s union on Sunday, the White House said after the union’s staff announced a strike.

The National Education Association Staff Union said it would strike on Friday, urging supporters to join them on a picket line outside the NEA’s convention in Philadelphia over the weekend.

“President Biden is a fierce supporter of unions and he won’t cross a picket line. The president is still planning to travel to Pennsylvania this weekend, and we will have more details to share at a later point,” the campaign said.

The union said it filed two unfair labor practice complaints with the National Labor Relations Board this week involving overtime nonpayment and unanswered information requests.

The NEA said misinformation had been shared about the ongoing contract negotiations but it remains committed to a fair bargaining process.

“NEA’s goal is to craft collective bargaining agreements with our staff unions that balance the interests of our members, affiliates, and staff while reflecting our mutual commitment to students, union values and racial and social justice,” a spokesperson said.

The representative did not comment on the Biden decision.

Biden will still travel to Pennsylvania this weekend, with details to be released later, the campaign said.

The National Education Association, with 3 million members, backed the Democratic president in his 2020 and 2024 presidential campaigns.

Biden, whose wife, Jill Biden, is a teacher and NEA member, calls himself the most pro-union president in history. He has supported a variety of measures to strengthen workers rights, including signing legislation to protect union pensions and other pro-union positions, since taking office in 2021.

In September, Biden joined members of the United Auto Workers (UAW) labor union on the picket line outside a General Motors (NYSE:) parts distribution center in Belleville, Michigan, and supported the union’s call for a 40% pay raise.

It was the first visit by a U.S. president to striking workers in modern history. The UAW endorsed him in January.

Biden and Donald Trump, his Republican rival in the Nov. 5 U.S. presidential election, are courting union votes in battleground states including Michigan, Wisconsin and Pennsylvania.