The Security Council's decision to authorize force against Iraq marks one of the most important turning points of the four-month-long Persian Gulf crisis, both for President Bush and Iraqi leader Saddam Hussein.

The world community has now declared its willingness to go to war if necessary to drive Iraq from Kuwait, or more specifically to support a U.S.-led military action in which Americans are likely to bear the brunt of the casualties.

The resolution is certain to intensify the diplomatic and military preparations on all sides in the next several weeks, bringing into even sharper focus the question of whether there will be war or peace in the Persian Gulf.

Soviet Foreign Minister Eduard Shevardnadze summed up the resolution's impact by saying it "gives time to think again. . . . At the same time, we are giving the victims in this crisis a firm pledge that they will not have to wait much longer, and help is on the way.

"Today we have started a countdown."

Ironically, while the Bush administration has been successful in gathering support abroad for the use-of-force resolution, backing for military action seems to be declining at home.

The U.N. vote came as the powerful Senate Armed Services Committee was holding hearings on the war-or-peace question featuring the testimony of several respected witnesses, including two former chairmen of the Joint Chiefs of Staff, who argued strongly for patience and for giving sanctions a long time, perhaps a year or more, to work before deciding that war is the only alternative.

Bush started the clock ticking three weeks ago by announcing a major new deployment of about 200,000 more troops to the gulf and deciding not to use those troops to replace ones already there. This has been widely interpreted as a direct threat to Iraq that war could come sometime between January, when the additional troops arrive, and March, when bad weather and Islamic religious holidays begin.

Now, the U.N. resolution starts another clock ticking for Saddam, virtually guaranteeing him that he will not be attacked by the U.S.-led coalition for the next six weeks but warning him that if he doesn't find a way to withdraw from Kuwait, he may face an internationally sanctioned attack any time thereafter.

The resolution is seen by its sponsors as a final effort to convince Saddam that the forces arrayed against him can now be used, and to provide a grace period for diplomatic maneuvering and for Saddam to consider his predicament and withdraw.

The Jan. 15 deadline does not mean that force will be used immediately after that date passes. But because military action against Saddam could come at any time after mid-January, it gives allied planners the element of surprise and means that Saddam will have to take account of that.

Until now, American civilian and military officials have indicated that their military forces were not prepared to take offensive action against the Iraqis.

The mid-January deadline also would allow the bulk of the additional 200,000 or so troops ordered into the region by Bush earlier this month to arrive in Saudi Arabia.

For Bush, the Security Council outcome provides a crucial victory in a determined, month-long, globe-trotting gamble by the president and Secretary of State James A. Baker III that they could marshal enough international support for a rare U.N. resolution condoning the use of force to get Saddam out of Kuwait.

The strong U.N. vote presumably will strengthen Bush's hand in dealing with mounting debate and opposition in this country, both in Congress and in the countryside, about the wisdom of going to war soon with Iraq rather than waiting for a much longer period to see if the economic sanctions and embargo against Baghdad will eventually force Saddam out of Kuwait without a war.

Although Bush and Baker had argued that there already were grounds to take action against Iraq under existing U.N. Charter rules, many others disagreed, and the administration clearly wanted firm backing for an unambiguous resolution pertaining to the current crisis.

The vote also dramatized the new post-Cold War world of U.S.-Soviet relations. While Moscow also has supported all the previous council resolutions demanding Iraqi withdrawal, the Soviet leadership had been strongly resistant to the endorsement of force. But now the Kremlin has been brought along into that coalition as well, with Soviet President Mikhail Gorbachev turning on Saddam in the last few days with the strongest language and sharpest warning he has ever issued to the Iraqi leader.

No one can predict what will happen in the next few months. But for Americans, especially, the reality of war will seem closer after yesterday's vote.