Mr. Biden’s transition team, a low-profile group of policy experts tasked with making sure the former vice president is ready to take office, has crafted alternative plans if President Trump—who has given mixed messages on whether he would commit to a peaceful transfer of power—refuses to comply with requirements that a president-elect’s team be allowed into federal agencies ahead of Inauguration Day. The team is also planning for a scenario in which the Trump administration declines to share resources or provide briefings seen as crucial for a smooth transition of power, the people said.

So far, these worst-case scenarios haven’t come to pass, people close to the Biden campaign and transition said, adding that the former vice president has received classified briefings and lower-level Trump administration officials have been professional in initial interactions with the team.

“Transition officials have been planning for various scenarios. So far, the pre-election process has run smoothly,” said a person familiar with Mr. Biden’s transition planning.

Asked for comment, a White House official said, “We’re following all statutory requirements.”