In remarks over the weekend to Telemundo, a Spanish-language network, Mrs. Pelosi said illegal immigrants must have notched serious criminal charges to merit deportation - contradicting federal law that says the presumption is against, not with, illegal immigrants.
"Our view of the law is that it - if somebody is here without sufficient documentation, that is not reason for deportation," she said in the interview, which an immigrant-rights group posted on its website. "If somebody has broken the law, committed a felony or something, that's a different story."
She becomes the highest-ranking Democrat to call for Mr. Obama to halt deportations while Congress is trying to work out a broader deal on an immigration bill that could provide legal status, and possibly a chance at citizenship, for most illegal immigrants.
Mr. Obama is increasingly facing pressure from his left flank over deportations.
On Monday, immigrant-rights activists protested outside of a U.S. Immigration and Customs Enforcement office in Fairfax, blocking a bus from leaving the facility for three hours. Just as police were breaking up that protest, another group began protesting outside an ICE office in Los Angeles.
Over the last two months, activists have blocked or delayed deportations in a dozen cities across the country, including in Mr. Obama's hometown of Chicago and in several locations in Arizona, which is ground zero for the immigration debate.
"Blaming Republicans can't stop the suffering in immigrant communities. But the president can," said Rosa Lozano, one of the protesters in Fairfax, in a statement issued by organizers. "With the stroke of a pen he could end his deportation quota and expand relief like he did for Dreamers."
The activists point to Mr. Obama's election-year decision to halt deportations for some young illegal immigrants - who call themselves "Dreamers" after the Dream Act bill - as a model. They say the president has the power to expand that non-deportation policy to most other illegal immigrants.
Mr. Obama has repeatedly said he doesn't have that broad a grant of authority - though before he used the power of prosecutorial discretion to let the "Dreamers" stay in the U.S., he also repeatedly denied that he could do that.
White House press secretary Jay Carney repeated that stance Monday.
"We have to enforce the law," he said. "Obviously, there is prosecutorial discretion, and that is applied. The focus is on those who've committed felonies."
In her interview with Telemundo, Mrs. Pelosi said she disputes that, saying she's appeared alongside some of those she said shouldn't have been deported.
"We have seen the personal stories. And we presented them to the administration," she said. "I'm hopeful that with the documentation that we are providing to counter what others may be saying about who's being deported, that we will see action from the president."
A spokesman for Mrs. Pelosi said her preferred option would be to pass a bill granting legal status to illegal immigrants, rather than relying on executive action. The spokesman said the California Democrat's stance on illegal presence in the country is a long-held position.
Still, immigration lawyers said her interpretation of the law is inaccurate and that those in the country without proper authorization are deemed deportable, and it's up to the individuals in question to prove they qualify for special consideration.