WASHINGTON – Rejecting an argument being made by some conservatives in his own party, President Bush said yesterday that the idea that America could force millions of illegal immigrants to return home “ain’t gonna work.”

Mr. Bush told a gathering of Hispanic leaders that the immigration system is broken and Congress needs to pass “commonsense” reform that strengthens the border while allowing more foreigners in to work temporarily and giving those who sneaked in years ago a chance to become citizens.

“There are those here in Washington who say, ‘Why don’t we just find the folks and send them home,'” Mr. Bush said. “That ain’t gonna work.”

He said although it sounds simple, it is impractical to insist that the 12 million illegal immigrants estimated to be living in America leave and come back legally. Some prominent conservatives in his party say allowing those immigrants to become citizens without returning home would amount to amnesty.

Mr. Bush defined amnesty as allowing those immigrants to automatically become citizens. He said instead they first should be required to prove that they have been working and abiding the law, pay a fine, learn English and wait behind those who have been in the country legally.

“We don’t have to choose between the extremes,” Mr. Bush said. “There’s a rational middle ground.”

Mr. Bush is trying to get Congress to pass his immigration plan, but a block of conservative lawmakers have been firmly opposed to it and prefer legislation that would take a harder stance against those who break the law to sneak in the country. House and Senate negotiators have yet to meet to resolve the differences in the two different approaches.