Defense spending next year is responsible and within limits, with most increases a result of the war against terror, Defense Secretary Donald Rumsfeld told a Senate panel Tuesday.

"When one combines the costs of inflation, plus the must-pay bills, plus realistic cost estimates for weapons, readiness and depot maintenance, the correct figure is $359.4 billion. When one adds to that the $19.4 billion in this budget for the war on terrorism, the total comes to $378.8 billion," Rumsfeld told the Senate Armed Services Committee.

President Bush has proposed a $48 billion increase to the defense spending bill for the next fiscal year, including an additional $18 billion for homeland security that would pay for anti-bioterror efforts and improved border control, among other things. The request is a 14 percent increase that would bring the Pentagon budget to $379 billion.

In the new spending for the war on terrorism, more than $1 billion is allocated to pay for fighter patrols over parts of the United States.

The overall budget also includes funding for the new joint strike fighter, a doubling of money for U.S. Special Forces and a 4.9 percent increase across the board for military pay.

The budget puts money into buying a new generation of stealth fighter jets and more precision munitions. It accelerates the development of unmanned planes, converts four nuclear submarines to vessels that can fire cruise missiles and insert special forces into battle, and invests in new combat communications systems.

Critics charge the administration is simply throwing more money at existing programs and is not making the tough transformation choices that had been promised. Rumsfeld countered Monday that he wants to shut down 25 percent of military bases, which are not needed but cost a lot to maintain, but everyone in Congress resists a base closing in his or her district.

Some Pentagon officials said that the budget reflects some arm-twisting by lawmakers to squeeze in pet projects that have nothing to do with the war on terrorism.

Rumsfeld said Tuesday the biggest military spending increase in two decades is needed to prepare U.S. troops for future wars even as they fight today's battle against terrorism.

Those tasks are made harder because the Pentagon also needs to rebuild after a "procurementless decade" that overused and underfunded the military.

"When the Cold War ended, a defense drawdown took place that went too far ... overshot the mark," Rumsfeld said. "Now, through the prism of Sept. 11, we can see that our challenge is not simply to fix the underfunding of the past."

Instead, Rumsfeld said, the Defense Department has three difficult missions at once — win the worldwide war on terrorism, restore forces with what he called long-delayed investments in weapons, personnel and facility improvements and transform the military for 21st century warfare.

"Our adversaries are watching what we do, they're studying how we have been successfully attacked, how we are responding and how we may be vulnerable in the future," he said of the aftermath of the terrorist attacks on America.

"And we stand still at our peril," he said.

Rumsfeld was appearing with the Joint Chiefs of Staff chairman, Air Force Gen. Richard Myers, to woo support for the budget plan President Bush submitted to Congress on Monday.

Committee chairman Sen. Carl Levin, D-Mich., opened the hearing by praising America's military performance in the campaign to root Al Qaeda terrorist and Taliban supporters from power in Afghanistan. But he sounded some years-old concern about Pentagon spending.

He said that although the war is rightly Rumsfeld's No. 1 priority, lawmakers also want to see a detailed strategy for transforming the armed forces and progress in improving financial management at the department infamous for decades of bad accounting and waste.

The Pentagon says it has spent about $7 billion so far on the war in Afghanistan, which began Oct. 7. The costs have grown so rapidly, officials say, that Rumsfeld already has decided he must ask Congress for more money as early as March.

Fox News' David Shuster and the Associated Press contributed to this report.