NEW YORK -- It's weeks before Thanksgiving but already interest groups are preparing for an intense conflict over Christmas observances by cities and public schools, with one conservative group lining up hundreds of lawyers to work on the issue.

Communities and courts have long fielded protests against municipal creche displays and school Nativity pageants, based on strict views of church-state separation and sensitivity toward religious minorities.

But in recent years, local disputes have extended -- to carol singing, wordless instrumental music, Christmas trees and decorations, classroom visits by Santa Claus, distribution of Christmas-themed cards and gifts, ''Merry Christmas!" greetings, and designation of Christmas on official calendars.

This week, the Alliance Defense Fund, a Christian legal group based in Scottsdale, Ariz., said its 800 cooperating lawyers have volunteered to handle without fee complaints about ''improper attempts to censor the celebration of Christmas in schools and on public property." In 2004, the second year of its ''Christmas Project," affiliated lawyers sent a detailed memo on the alliance's view of Christmas and constitutional law to 7,000 school districts. The 2005 effort, already underway, adds city officials.

A similar information campaign is being waged by Liberty Counsel, another Christian legal group based in Orlando, Fla., and the Christian Educators Association International, representing 8,000 public school teachers.

The topic also is the subject of a polemic by John Gibson of the Fox News Channel that is selling briskly: ''The War on Christmas: How the Liberal Plot to Ban the Sacred Christian Holiday Is Worse Than You Thought."

Gibson, who calls himself a ''non-practicing Christian," notes that his Jewish son researched the book. He says agitation against Christmas observance comes primarily from ''secularists, so-called humanists, trial lawyers, cultural relativists, and liberal, guilt-racked Christians."

ACLU religion director Jeremy Gunn was in meetings and unavailable for comment, a spokeswoman said. But an official ACLU bulletin says the Constitution forbids school observances ''that promote or emphasize the religious significance" of Christmas, but not aspects ''that have become part of our country's secular culture."

Under Freedom Forum First Amendment Center sponsorship, the ACLU has come to agreement with evangelical and other religious groups on minimal rules about school religious issues. On holidays, the accord says schools may celebrate secular aspects and ''objectively teach about their religious aspects" but not observe them as religious events. Americans United for Separation of Church and State endorsed the accord.