WASHINGTON/ISLAMABAD (REUTERS) ? The United States sought to build confidence in its drive against global terrorism on Wednesday, lining up international diplomatic support while preparing new safety measures to coax nervous Americans back onto airplanes.

In New York, as hopes dimmed that any of the 6,347 people listed as missing after the Sept. 11 attack on the World Trade Center could still be found alive, families began registering for death certificates in grim acknowledgment that their loved ones probably perished in the collapse of the city’s tallest buildings.

As U.S. forces massed for possible strikes against Afghanistan, protesters set fire to the abandoned U.S. Embassy in Kabul and the leader of the hard-line Taliban pledged continued defiance of U.S. demands to hand over fugitive Saudi-born militant Osama bin Laden ? the man Washington says was behind the devastating attacks.

“Even if it (the United States) were twice as strong, or twice that, it would not be strong enough to defeat us. We are confident that no one can harm us if God is with us,” Mullah Mohammad Omar said in an interview broadcast on Wednesday.

Economic fears continued to reverberate around the world as policy makers from leading industrial nations fought to battle growing pessimism on the prospects for growth.

The U.S. stock market, which rebounded earlier this week after posting its worst one-week drop since the Great Depression of the 1930s, resumed its downward slide as more airline layoffs and corporate earnings warnings sent skittish investors running for cover.

BUSH SET TO UNVEIL AVIATION SECURITY PLAN

Those fears have been greatest in the aviation industry, which has been forced into financial crisis following attacks that saw four hijacked commercial passenger planes turned into deadly missiles.

Delta Air Lines Inc., the nation’s No. 3 carrier, became the latest airline to announce major job cuts on Wednesday, saying it would lay off 13,000 people, or 16 percent of its workforce. The Delta cuts pushed the total number of airline layoffs to well over 100,000 as the industry struggles with plunging travel demand in the wake of the attacks.

In response, President Bush said he would unveil a package on Thursday aimed at getting wary travelers back in the skies ? slating such security improvements as stronger cockpit doors and more armed “sky marshals.”

“One of my concerns is that this terrible incident has convinced many Americans to stay at home. One of the keys to economic recovery is going to be the vitality of the airline industry,” Bush said.

COALITION TAKING SHAPE

In Washington and in Europe, U.S. officials sought to give greater shape to the coalition against terror while keeping a tight lid on what military options the United States was considering as it masses warplanes, ships and troops within striking distance of Afghanistan.

U.S. Deputy Defense Secretary Paul Wolfowitz met with NATO defense ministers in Brussels, and then told reporters it was unlikely the United States would request full NATO action in the coming conflict.

“If we need collective action, we’ll ask for it. We don’t anticipate that at the moment,” he said, playing down expectations of imminent or spectacular U.S. military action.

Secretary of State Colin Powell said on Wednesday that Bush would also consider seeking additional U.N. support for military strikes ? although he stressed that Washington believed it had the right to defend itself.

But while the United States has successfully isolated Afghanistan’s Taliban, there were already signs of trouble in its drive to put together solid international backing for military action against bin Laden and his al Qaeda network of Islamic militants.

Western hopes that Iran might join the coalition against bin Laden and his Taliban hosts were dashed on Wednesday when Iranian Supreme Leader Ayatollah Ali Khamenei angrily vowed that his country could take no part “in an attack on suffering, neighboring Muslim Afghanistan.”

“We do not believe America is sincere enough to lead an international move against terrorism. America has its hands deep in blood for all the crimes committed by the Zionist regime,” he said, referring to Israel.

Egypt, one of Washington’s closest Arab allies, also voiced doubts as Egyptian Foreign Minister Ahmed Maher said that Washington should make its case to the international community before embarking on military action.

“We believe that the United States, as the government of a country that believes in law and justice, will act on the basis of a case, a good case ? because I am sure they have a good case,” Maher told reporters after meeting Powell on Wednesday.

U.S. GRIEF FOR THE VICTIMS

Across the United States, people continued to grieve for the nearly 7,000 people feared killed when hijacked airliners slammed into New York’s World Trade Center and the Pentagon near Washington in choreographed attacks. Another hijacked jet crashed in Pennsylvania, killing all on board.

In Boston, more than 20,000 people crowded City Hall Plaza for a memorial service for the crews aboard American Airlines Flight 11 and United Airlines Flight 175, both of which were hijacked from Boston’s Logan Airport.

While rescue workers picked through the ruins of the World Trade Center’s 110-story towers, hundreds of people went to a New York assistance center to apply for death certificates necessary to claim life insurance and other death benefits for the missing.

“Now we’ll have a memorial service to say goodbye,” Alfredo Bordenabe said after applying for a death certificate for his wife, Crystine, who was eight months pregnant and worked at an investment bank in World Trade Center.

“You can’t hold out hope when they say there are probably no survivors. My heart doesn’t skip a beat anymore when the phone or the doorbell rings. And this is the main way to get closure,” he added.

ECONOMIC FEARS GRIP WEST, AFGHANISTAN IN CRISIS

Hopes for a quick recovery seemed to recede as ratings agency Standard & Poor’s said the attack would push the United States into recession and halt global economic growth in the coming quarters.

The International Monetary Fund, for its part, issued a report saying the attacks added “further increased downside risk” to an already slow U.S. economy.

Policy makers from leading industrial nations including Italy and Germany have voiced confidence that growth can continue despite war fears and plunging consumer confidence.

But U.S. consumer sentiment ? the engine behind the world’s largest economy ? looked shaky at best, with several studies showing it at or near recessionary levels.

The situation in Afghanistan was far worse. Already one of the poorest countries in the world, Afghanistan faces a ”stunning” humanitarian crisis as the threat of U.S. military strikes exacerbates already tenuous conditions, six U.N. agencies said in a joint statement.

They said war fears could drive another 1.5 million Afghans to flee the country, joining 3.5 million who have already sought refuge in Iran and Pakistan in recent years.

In Kabul, angry Taliban supporters torched the U.S. Embassy building abandoned since 1989 ? axing down doors and starting fires while declaring support for Islam and bin Laden, who has lived in Afghanistan as a “guest” for some five years.

The Taliban’s leader, Mullah Mohammad Omar, told his people they should not join the exodus of refugees, saying America ”has no reason, justification or evidence” for attacking Afghanistan.

The Taliban has recommended bin Laden leave the country, but has said it cannot find him to deliver the news.

In an ironic twist, Omar was given air time by Voice of America (VOA) radio on Wednesday as it broadcast a rare interview with the reclusive leader despite State Department objections that the taxpayer-funded broadcaster should not be used to propagate his views.

“This is not just an issue of Osama bin Laden. This is an issue of Islam, Islam throughout the world. Islam’s prestige is at stake,” Omar said on VOA.