President Bush intensified his lobbying for the $500 billion deficit-reduction plan last night, warning that the package of tax increases and spending cuts is needed to keep the economy out of recession and appealing to voters not to punish politicians who support it.

As White House officials reported steady progress in their efforts to rally rebellious Republicans, Bush delivered a nationally televised speech from the Oval Office in which he said that, despite its flaws, the new budget plan is the best that bipartisan government can deliver.

"Those who dislike one part or another may pick our agreement apart, but if they do, believe me, the political reality is, no one can put a better one back together again," he said.

The evidence of bipartisanship came moments later when Senate Majority Leader George J. Mitchell (D-Maine), delivering the Democratic response, echoed the president's call, saying that while it demands sacrifice, the package "holds the promise of restoring a sound economy from which all Americans will benefit."

Pointing out that Democrats had made compromises to reach the agreement, Mitchell took note of Republican opposition. "We hope that . . . Republican members of Congress will also set aside partisan differences, as we have done, and join us in doing what's right for our country," he said.

Bush and top administration officials met throughout the day with Republicans from the House, where the defection of Minority Whip Newt Gingrich (R-Ga.) and other key conservatives set off initial fears at the White House that the package might be defeated by a mutiny in the president's own party.

After hearing from these members yesterday, Bush suddenly decided to schedule last night's televised address. Aides said it was designed primarily to provide politicians suffering from election-year jitters with the presidential cover they may need to support the plan.

Although many Republicans dislike the package, especially the new taxes that break Bush's 1988 campaign pledge, increasingly they are concluding they may have no choice but to support it.

"There is no alternative," Rep. Don Sundquist (R-Tenn.) said after meeting with Bush. "The alternative is chaos and the alternative is recession, or even depression."

White House officials met with 40 to 50 House Republicans yesterday, and at least one more meeting is scheduled today. "We made very significant progress since {Monday}," a White House official said. "But we do not have the votes."

Nevertheless, one leading conservative opponent of the package, Rep. Vin Weber (R-Minn.), flatly predicted the president's lobbying efforts would be successful. "Sure he's going to win," Weber said. "Anybody who thought that you were going to beat a president in his own party's caucus . . . is fooling himself."

The House is scheduled to take its first votes on the budget agreement on Thursday. The Senate, where support appears much stronger, is expected to follow shortly after that. The first votes will be on the budget resolution itself, along with orders to congressional committees on the targets they must meet.

A second and perhaps more critical round of votes will come later, after the committees have concluded their work and the pieces are stitched back together into one large package.

Bush asked Americans to understand the plight of politicians seeking reelection. "Many worry about your reaction to one part or another," he said. "But I know you know the importance of the whole."

He said voters could have a "real impact" by registering their support with their elected representatives.

Bush called the package tough and fair with spending cuts that will be enforced by law. "No smoke, no mirrors, no magic act," he said.

He said the package does not raise income tax rates, "does not mess with Social Security" and protects national security. Saying he was no fan of new taxes, Bush said some of the taxes in the package will help to create jobs and stimulate the economy, while requiring that everyone "contribute something" to the fiscal solution.

"If we fail to enact this agreement, our economy will falter, markets may tumble, recession will follow," he said.

With it, he predicted lower interest rates and an end to "the cancer gnawing away at our nation's health."

White House officials said concern over the economy had helped persuade Bush to go on television to fight for the package. "If the budget agreement doesn't pass, we tube the economy," one official said. "We're very worried about the market's reaction and the consequences of shutting down the government."

Mitchell underscored the difficult negotiations by noting there were still "deep differences" between Republicans and Democrats over how best to solve the fiscal crisis. The Democrats, he said, preferred a package that "asks more from the wealthy and less from the elderly," the last being a reference to the deep cuts in Medicare that have been roundly attacked by senior citizen organizations.

The House Ways and Means Committee issued a study yesterday showing that the tax increases and benefit program cuts would hit hardest at the poor. The average taxpayer in the poorest fifth of all taxpayers would have after-tax income reduced by 2 percent under the agreement. The after-tax income of the average taxpayer in the richest one-fifth would be reduced by only 0.9 percent, the panel's study found.

But despite Democratic differences with the package, Mitchell said "the nation is more important than partisan differences" and urged the public to join Democratic congressional leaders and Bush in backing it.

House Republicans remained in an uproar over the package. One said the administration appeared "stunned at the level of ill-will among Republicans over this."

The White House was fighting not only conservative criticism of the package but reaction to harsh comments by White House Chief of Staff John H. Sununu. The White House staff chief warned House Republicans on Monday that Bush might come into their districts to hold them accountable if they vote against him. Later he drew criticism for referring to Sen. Trent Lott (R-Miss.) as "insignificant."

"It's Beirut over there," one Democratic aide said.

Initially alarmed by the Republican reaction to the package, White House officials sounded far more upbeat by late yesterday. With Vice President Quayle, Sununu, budget director Richard G. Darman and Treasury Secretary Nicholas F. Brady helping Bush apply the pressure, the administration appeared to stem its losses, even though many members said they were still undecided how to vote.

"Loyal Republicans need to support the president at a time when his prestige is on the line," Rep. E. Thomas Coleman (R-Mo.) said after meeting with Bush.

Rep. Bill Archer (R-Tex.), ranking Republican on Ways and Means, got special hand-holding, including a private meeting with Sununu, Darman and Brady and then a one-on-one with the president. Yesterday afternoon, he announced he would support the package.

Staff writer Ann Devroy contributed to this report.