Crawford, Tex. ? President Bush has nearly doubled the size of the economic stimulus package he will propose next week in an effort to jumpstart the economy ahead of his re-election bid, administration officials said Friday.

Republican officials said the White House had repeatedly signaled that the package, to be announced by Bush in Chicago on Tuesday, would cost $300 billion over 10 years. But a senior administration official said Friday that Bush would announce a package costing $500 billion to $600 billion over a decade.

Democrats attacked Bush’s plan even before it was announced.

House Minority Leader Nancy Pelosi, D-Calif., questioned Bush’s plan to cut taxes on stock dividends, saying that it would favor the wealthy.

In her first news conference as leader, Pelosi said much of the tax package would benefit the rich. She said 25 percent of the dividend tax credit would go to Americans earning $1 million a year and that some of the companies that would benefit from it do not pay taxes.

“The thought that this helps the American people is an illusion,” she said.

The components of Bush’s plan appeared to remain somewhat in flux. Bush approved key parts of the plan at his ranch here Friday before visiting troops at nearby Fort Hood, officials said. He will make decisions about the rest of the package this weekend or on Monday, the officials said.

The tax cuts in the package — including a reduction in the tax of stock dividends, and an acceleration of income tax cuts passed last year — will cost more than $300 billion, the senior official said. Other parts of the package include an extension of unemployment benefits.

Pelosi said the plan to extend unemployment benefits was “too little, too late, but we’ll just see how little it is.”

A Republican official said the White House appeared to be counting money that likely would have been spent anyway, including federal aid to states, to make the package seem larger. A White House official replied that the $300 billion estimate, widely expected by Republican lawmakers, had always been premature. Bush’s new economic adviser, Stephen Friedman, is scheduled late next week to visit Wall Street to promote the plan.

Pelosi’s sharp criticism of the president’s economic plan signaled her determination to draw distinctions between the two parties. “The American people expect and deserve the members of Congress to find our common ground where we can for the American people,” she said. “But where we cannot, they expect us to stand our ground.”

Pelosi did not disclose any details of the House Democrats’ economic stimulus package, which she plans to unveil Monday. She ruled out a payroll tax holiday, however, saying that would drain funds from the Social Security trust fund.

According to Democratic officials, the package includes a tax rebate for families.