MEXICO CITY - Wearing tennis shoes and jeans, Saul Arellano, 7, walked the halls of Mexico's federal Congress on Monday like a young lobbyist, speaking to lawmakers about his fight to keep his mother from being deported from the U.S.

The second-grader has been living with his mother, an undocumented Mexican migrant, at the Adalberto United Methodist Church on Chicago's West Side since Aug. 15 when she was scheduled to surrender to U.S. authorities for deportation.

"I want my mom to stay with me in the U.S.," Saul said in an interview with The Associated Press in between meetings with Mexican lawmakers. "I want to stay there because that is where my school is."

Saul, who bought a new tan suit, planned to address the Mexican Congress during its regular session on Tuesday. Several lawmakers who met with him informally on Monday said they would present a resolution to help the family by asking their U.S. counterparts to stop Elvira Arellano, 31, from being deported.

So far, U.S. immigration authorities have made no attempts to arrest Elvira Arellano, but she knows she could be arrested at any time.

The single mother's fight is being closely watched by legal experts and immigration activists on both sides of the border as it could affect more than 3 million children who are U.S. citizens but who have at least one parent in the country illegally.

While his mother stays inside the church as friends bring her food and clothes, Saul has taken her battle to the outside world.

Over the past few months, he has been speaking at conferences from Chicago to Los Angeles and written letters to top U.S. political figures, including U.S. President George W. Bush. This is his first visit to Mexico and he hoped to meet his grandparents in central Michoacan state for the first time.

"I told President Bush to stop the deportations so families can stay together in the U.S.," he said.

Saul said he was scared to come to Mexico "because when I'm here they could deport my mom."

But "she told me to behave and be brave," he said.

"I still don't know what I'm going to say (to the Congress)," he admitted. "I've been walking around thinking."

Activist Emma Lozano, the executive director of the Chicago-based immigration-rights group Centro Sin Fronteras who accompanied Saul, said lawmakers were touched by the boy.

"They were really moved by his words," he said. "He's so small but he really seems like he can handle an interview. He's been biting his nails a little bit. But I told him 'you don't need to be nervous, you're among friends."'

Elvira Arellano wrote a letter to Mexican President Vicente Fox but has not received a response from the leader, who is set to leave office Dec. 1.

"It's not just about me. I am the example for what thousands of Mexican families face here," she told the AP in a telephone interview from Chicago.

Elvira Arellano has said that if she is deported, it would deprive her son of his rights as a U.S. citizen.

The U.S. Border Patrol caught the migrant worker from central Michoacan state in 1997 shortly after she crossed the border. She crossed again and made it to Chicago, where five years later she was arrested and convicted of working as a cleaning woman at O'Hare International Airport under a false Social Security number.