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 did not immediately return a request for comment.

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.

(Reporting by Doina Chiacu and Nandita Bose; Editing by Josie Kao)