President Bush ordered a massive new military escalation in the Persian Gulf on Thursday because Iraqi President Saddam Hussein was not "taking us seriously," a senior administration official said yesterday, and U.S. advisers concluded that a greater show of strength is needed to convince him that the United States and other nations will not wait indefinitely to force him out of Kuwait.

Other top U.S. officials said the near doubling of the military deployment was prompted as well by the U.S. military's rising concerns about getting into a prolonged, tense armed stalemate in the desert with Iraq and by increased doubts that economic sanctions alone can force Iraq's withdrawal. The new troops will add about 200,000 to the 230,000-strong U.S. force now in the gulf.

The senior official, who spoke on condition that he not be identified, said that neither the economic sanctions, the various U.N. resolutions condemning Iraq, nor the multinational force now arrayed in the gulf have convinced Saddam that he risks war if Iraq does not relinquish Kuwait, which it seized on Aug. 2.

"Clearly he's still playing games -- and some of them with some skill -- trying to divide the coalition, as if time is on his side," the official said.

The senior official said Bush's decision should not be seen as a dramatic change in U.S. policy, but as a further step in assuring the original goal of confronting Saddam's aggression, peacefully if possible.

"What we are trying to do is tell Saddam Hussein, 'Look, we are serious.' We intend to prevail on this because the consequences of failing -- for the United States, for the coalition, for the United Nations -- are pretty catastrophic," he said.

The official conceded that the new deployment could bring the possibility of conflict closer, in part because of the difficulties of keeping U.S. forces sharp for an extended period of time and because of the potential cracks in the international coalition if the crisis drags on.

"It's tough to keep an edge on your forces out there as weeks go into months and morale goes down," he said.

But the administration is not yet prepared to issue an ultimatum, the official said. "We're still hopeful he'll come to his senses."

Defense Secretary Richard B. Cheney said the new deployment ends any possibility of rotating units soon. "They are not going there as replacements, but rather to be added to the forces that are already present," he said.

Among the military facets of the new deployment were the desire of senior defense officials to deploy new forces before the usual February rains and March sandstorms in Saudi Arabia and Kuwait that would complicate a U.S. offensive. One official said the seasonal rains in Kuwait and Iraq would mean that the desert alliance's forces would advance on "worse and worse terrain."

The force of up to 200,000 additional troops and associated military equipment is unlikely to reach the region until early January, and thereafter setting up what military officials call a "two-month window" of opportunity for a possible offensive.

"You have to act to make your force credible now, it seems to me, given the weather circumstances" next year, said Rep. Lee H. Hamilton (D-Ind.), chairman of the House Foreign Affairs subcommittee on the Middle East.

He and others also said any U.S. military action during Ramadan, the Islamic holy month that begins in mid-March, would be complicated by the presence of thousands of religious pilgrims in Saudi Arabia and by strict daytime fasting rules for allied Arab troops.

"These are all elements of the equation," a senior military official said. "It doesn't mean, however, that just because we will have a {larger} force in place before bad weather or a religious celebration that we should do something."

The timing of the new deployment also was dictated in part because the initial buildup was nearly complete, freeing ships and planes for transport, and administration officials had concluded weeks ago they wanted more forces.

In contrast to the views of other officials who were interviewed, the senior administration aide maintained that the new deployment is not related to the sanctions, "only that we're not prepared to give the guy unlimited time . . . . It's probably still early to come to any conclusion about the extent to which sanctions are working. Clearly, the sanctions are not at the point now where he is seriously constrained."

While maintaining a commitment to the sanctions, it is clear the United States is not ready to wait for the sanctions to create massive food shortages and bring wide suffering to Iraq's 18 million people.. "Starving them out creates additional problems," he said.

The decison to expand the U.S. forces also was in response to Saddam's doubling his forces in Kuwait to about 450,000. Although Bush said in August he was sending forces to defend Saudi Arabia, administration officials understood that any military clash with Iraq would require more troops.

If there is conflict, U.S. military planners wanted a force large enough to finish the job, rather than the policy of gradualism that marked the U.S. involvement in Vietnam.

While the three-month-old sanctions have slowed Iraq's economy and pinched supplies of military spare parts, administration officials consider them unlikely to cause enough shortages of commercial and industrial goods to stir public unrest before next spring.

"Saddam has such discipline over his population {that} it could take months and possibly even a year before it gets so bad that he will pull out," said Phebe Marr, an Iraqi scholar at the National Defense University.

A senior defense official agreed, saying "there's a lot to be said against dragging this out. There are dangers in it, including the prospect of terrorism {against U.S. forces} or a likelihood that people will begin to accept it as a fait accompli."

The senior administration official, saying the Vietnam War was fought under conditions favorable to the Viet Cong and North Vietnamese, rejected any comparison with the gulf confrontation. A war with Iraq would be conducted in a way to maximize U.S. military capabilities. "He can't hide under the trees," the official said.

The aide said no prospect of a diplomatic solution has surfaced. "There is no one . . . who's come back and said, 'We're hopeful,' " the official said. "Even those desperately wanting to find some avenue have not said they're finding any light . . . . "

While the administration will continue consultations with allies that Secretary of State James A. Baker III began on his recent trip to the gulf, the Soviet Union and Europe, Bush believes he already has the authority to go to war under the U.N. charter.

"To hold together a coalition as disparate as this one {for that period of time} is difficult," a U.S. official said. "There is a risk that Saddam will strike a responsive chord by letting some of the hostages go or that he will play different countries against each other."

Congressional sources said yesterday it is uncertain how much the latest deployment will add to the estimated $15 billion cost so far of Operation Desert Shield. They said the amount depends on how long the reservists are on the active-duty payroll, whether they are deployed to the Middle East, and other factors.

The 101st Congress approved $3 billion for gulf operations, and the recently passed 1991 defense spending law appropriates another $1 billion from the Pentagon's "Defense Cooperation Account," money contributed by other countries such as Saudi Arabia and Kuwait.Staff writer Dan Morgan contributed to this report.