The president announced his funding request to Congress in a nationwide address Sunday night in which he said Iraq was now the "central front" in the war on terrorism.
"We are fighting that enemy in Iraq and Afghanistan today, so that we do not meet him again on our own streets, in our own cities, "Mr. Bush said.
The money "is about the safety and security of the American people," said White House spokesman Scott McClellan on Monday. He said the situation is "at a critical moment."
The request appeared to have brought to a head months of doubts over the war.
Mr. Bush's money request — surpassing earlier unofficial estimates — would come on top of the $79 billion that Congress approved in April for the initial costs of the war and its aftermath and for worldwide efforts against terrorism.
Mr. Bush said that roughly $66 billion of the $87 billion he will seek from Congress for the fiscal year starting Oct. 1 is for military and intelligence operations in Iraq, Afghanistan and elsewhere. Earlier cost estimates of the terrorism war had ranged between $60 billion and $80 billion.
Of the nearly $66 billion, $51 billion would be for Iraq, $11 billion for Afghanistan and about $200 million for the Horn of Africa, a congressional official knowledgeable about the request said Monday.
This source also said that $1.5 billion would be used for U.S. support of foreign troops participating in stabilizing Iraq; $5 billion for security there and $15 billion for work on restoring and upgrading the nation's infrastructure. Another $2.2 billion would be set aside for reserve mobilization, if necessary, said this official, speaking on grounds of anonymity.
Defense Department officials have previously said U.S. operations are costing about $3.9 billion monthly.
A fresh burst of Democratic criticism followed the speech.
Sen. Carl Levin of Michigan, the senior Democrat on the Senate Armed Services Committee, said Congress will approve the money needed to support U.S. troops, but that lawmakers want the president to tell them what his "exit strategy" is from Iraq.
Mr. Bush has "been going down the wrong path," said Rep. Dick Gephardt, D-Mo., a White House hopeful.
Howard Dean, another Democratic candidate, on Monday accused Mr. Bush of going into Iraq "recklessly" and said on NBC that "failure is not an option."
However, Sen. Richard Lugar, chairman of the Senate Foreign Relations Committee, praised the president's "courageous leadership."
The Congressional Budget Office projected that the U.S. would spend $452 billion on defense in the coming fiscal year. The president's new request would increase that amount by more than 19 percent. It comes as estimates for next year's budget deficit breach $500 billion.
McClellan says Mr. Bush still believes he can cut the deficit in half in five years if Congress "holds the line on spending elsewhere," but wouldn't elaborate.
Sunday's address was the president's first major speech on Iraq since May 1, when he stood on the deck of the aircraft carrier Abraham Lincoln and declared an end to major combat operations. Since then, more Americans have died in Iraq than were killed during the war. The overall death count is 287 — 149 since May 1.
The speech was an acknowledgement that Mr. Bush's Iraq policy is in trouble as reflected by polls, which indicate Americans have growing doubts, reports CBS News Correspondent Mark Knoller.
The attacks on American forces continued Monday when an explosion struck a U.S. patrol convoy near the center of Baghdad. Two soldiers were wounded, a military spokesman said.
Republicans and Democrats alike have urged Mr. Bush to change course and seek more troops and money from other countries. But Mr. Bush said the current number of U.S. troops in Iraq — 130,000 — is sufficient but that more foreign troops are needed.
He said two multinational divisions, led by Britain and Poland, are serving alongside the United States, and that American commanders have requested a third multinational division.
On Monday, Britain's Ministry of Defense said that country will send two additional battalions to Iraq, adding 1,200 troops to its forces already there. Britain has 11,000 troops in the country.
Some countries have asked for an explicit U.N. peacekeeping authorization, and Mr. Bush said Secretary of State Colin Powell would seek a Security Council resolution to authorize deployment of new forces.
Questions also have been fueled by the administration's failure to find any of Saddam Hussein's alleged illegal weapons or Saddam himself. The president made only passing reference to the alleged arsenal last night, a stark contrast to his claims before the war. Al Qaeda leader Osama bin Laden is also still at large.
"We will eventually bring to justice the entire al Qaeda leadership, and Saddam Hussein himself, too, I fully believe, will be found, but we have to keep our eye on the ball," national security adviser Condoleezza Rice told the CBS News Early Show.