Washington ? The Bush administration is moving forward aggressively with planning to oust Iraqi leader Saddam Hussein, laying the groundwork for a possible U.S.-led invasion early next year, according to senior U.S. officials and individuals involved in the planning.

Under one scenario being discussed at the Pentagon, a force of 250,000 to 300,000 U.S. troops would invade Iraq and overthrow Saddam, backed by massive airstrikes. Turkey, Kuwait and Qatar have indicated they would allow their territory to be used for an attack.

But some civilian aides to Defense Secretary Donald Rumsfeld are pushing for a quicker and, critics say, riskier thrust in an attempt to catch Saddam off guard. That strategy would involve roughly 80,000 troops and could be in place by this fall.

“If it happened in October, I wouldn’t be completely surprised,” said one official involved in the planning. He and others spoke on condition of anonymity.

Proponents of this approach argue that a surprise attack is vital because the Iraqi leader knows that, unlike the 1991 Persian Gulf war, the U.S. goal this time will be his ouster. Thus, he may be tempted to lash out first with chemical or biological weapons.

What Saddam might do is at the center of the debate about which plan to follow. Some could start earlier than others, a senior U.S. official said. Large numbers of Americans and Iraqis could be killed and wounded, especially if there was fighting in Baghdad and other major cities.

President Bush who has repeatedly declared his intention to get rid of Saddam has made no final decision on which, if any, plan to execute, the officials emphasized.

And the White House has not yet begun a concerted effort to convince the U.S. public, Congress or American allies of the need to pre-emptively strike Iraq.

“It is absolutely clear to me they have not made the case yet, and they know that. They haven’t made it to the American people, they haven’t made it to our allies, and they haven’t made it to the region,” said Sen. Joseph Biden, D-Del. Biden, chairman of the Senate Foreign Relations Committee, opens hearings on Iraq policy next week.

Washington’s two closest Arab allies, Egypt and oil-rich Saudi Arabia, oppose military action against Iraq, as does virtually every European ally except Great Britain.

These nations argue that Bush should first get the Israeli-Palestinian conflict on a path to resolution. Otherwise, they say, attacking Iraq could ignite the Middle East and endanger pro-Western regimes.

The State Department shares those concerns. “With all that’s going on, with all the uncertainty in the Middle East … it probably is not a good time,” said a senior State Department official.

Nor has the Bush administration sketched out a vision of a post-Saddam regime that could hold together the unruly nation of 23 million Shi’ite Muslims, Sunni Muslims and ethnic Kurds.

Despite these unanswered questions, the United States appears to be creeping toward war. Some officials worry that Bush may have backed himself into a corner with his bellicose rhetoric.

In another possible sign of Bush’s intent, the United States moved this week to shut down U.N. negotiations with Iraq over a return of weapons inspectors.

U.N. Secretary-General Kofi Annan told the Security Council on Wednesday that further talks with Iraq would be fruitless unless Baghdad agrees to give inspectors unconditional access. Washington opposed even technical-level talks with the Iraqis, a U.S. diplomat said.

The move prompted speculation that Washington was preparing public opinion for an eventual attack.

No attack is imminent, British Prime Minister Tony Blair said Thursday. “There are many issues to be considered before we are at the point of decision,” he said.

But Blair added that “the omens don’t look very good, frankly,” for a diplomatic breakthrough.