He said that will never happen without Republican support, pleading: "I need some help."
In asking anew for an immigration overhaul, Obama showed solidarity with his guest of honor, Mexican President Felipe Calderon, who called Arizona's law discriminatory and warned Mexico would reject any effort to "criminalize migration."
The United States and Mexico share a significant economic and political relationship that stands to be damaged the more the nations are at odds over immigration, which affects millions.
Obama sought to show that he, too, is fed up with the government's failure to fix a system widely seen as broken. He said that would require solving border security, employment and citizenship issues all at once - the kind of effort that collapsed in Congress just three years ago.
The president's stand underscored the forces working against him in this election year: the need for help from Republican critics, the impatience of states like Arizona after federal inaction, the pressure to show movement on a campaign promise, and the mood of the public disgusted by porous borders.
The Arizona law requires police to question people about their immigration status if there's reason to suspect they're in the country illegally, and it makes it a state crime to be in the United States illegally. Yet in a Rose Garden appearance with Calderon, Obama called the Arizona law "a misdirected expression of frustration." He expects to announce soon what action his government may take about it, once the Justice Department finishes reviewing whether the law violates civil rights.
Calderon was upbeat about finally finding a fair, dignified way of dealing with migrants. He added: "Many of them, despite their significant contribution to the economy and to the society of the United States, still live in the shadows, and occasionally, as in Arizona, they even face discrimination."
The immigration theme dominated a day of pageantry and showy support for Calderon, who enjoyed a state visit with his wife, Margarita Zavala.
The Mexican president was treated to a grand welcome on the South Lawn in the morning. Last night, 200 guests were invited for a state dinner in the East Room followed by entertainment back on the lawn under cover of an enormous tent.