Megachurch pastor Rick Warren attended a large Reform Jewish gathering last week to share tips on how to build a community.

Warren - who saw his church expand from just seven people meeting in his house to 22,000 people worshipping in an expansive treasure island-like campus - said the key to holding onto visitors was involving them in a small group.

"We believe congregations have to grow large and small at the same time," Warren said Thursday, according to the San Diego Union-Tribune newspaper. "We don't really feel like people are in the congregation until they're in small groups."

The "Purpose-Driven" pastor spoke to thousands of Jewish leaders Thursday night at the Union for Reform Judaism's biennial convention in San Diego.

With the holiday season in mind, Warren urged clergy to take advantage of crowded events to publicise other programmes so people can get involved in the community through smaller groups.

"There are some principles that apply regardless of our faith, if it's Jewish or Christian," he said at the convention.

One of his principles: "Just be nice to people. Smile."

After Warren spoke a few minutes at the podium, he sat alongside two popular Southern California rabbis for a casual talk about strengthening congregational life.

Other advice given by Warren included looking at everything from an outsider's viewpoint, such as simplifying worship terms, making strangers feel welcome, and encouraging interaction.

"The congregation that really loves people, you have to lock the doors to keep people out," said Warren, whose Saddleback Church in Lake Forest, Calif., is scheduled to host 14 Christmas services this year with an estimated crowd of 45,000 people.

The biennial meeting of the largest Jewish denomination in North America began December 12 and concluded on Sunday.

Other guests at the conference included the Rev Jim Wallis of Sojourners and Dr Ingrid Mattson, president of the Islamic Society of North America.