June 28 (Bloomberg) -- An unreliable ally in a U.S.-led war against guerrillas, declining public support at home and lack of a coherent exit strategy: That was Vietnam 35 years ago, and it increasingly seems to fit Iraq today.

President George W. Bush insists there must be no timetable for a withdrawal of 135,000 U.S. troops, and even many critics of his policy concur. Bush will try to restore Americans' confidence in his plan in a speech tonight at Fort Bragg, North Carolina.

Bush outlined his strategy yesterday: laying the political foundation for a democratic Iraqi government while training enough Iraqi troops to secure it so U.S. forces can go home.

``The key to success in Iraq is for the Iraqis to be able and capable of defending their democracy against terrorists,'' Bush said after a White House meeting with German Chancellor Gerhard Schroeder. Bush is likely to echo this message tonight in the face of some of the deadliest insurgent attacks and most anxious assessments of the war since Saddam Hussein was toppled more than two years ago.

Bush's speech tonight will talk ``about why we shouldn't be setting timetables'' for withdrawal of U.S. troops, and will reassert the president's goal ``to complete the mission,'' spokesman Scott McClellan told reporters today. ``He will be talking about the strategy for success.'' Bush will first spend more than two hours meeting with families of 33 fallen soldiers.

`Make Changes'

Some Republicans in Congress, nervously eying the 2006 elections, sound like Democrats when they critique the president's policies. ``We're going to have to make changes or we will lose,'' Nebraska Senator Chuck Hagel told an American Legion meeting June 25 in Grand Island, Nebraska. Americans don't want ``another Vietnam,'' Hagel said, according to the Omaha World- Herald.

More and more Republicans, including some conservatives, echo these concerns, which have been stoked by comments such as Defense Secretary Donald Rumsfeld's June 26 comments that the insurgency could last as long as 12 years.

More than 1,700 U.S. soldiers have been killed and 6,400 wounded in the conflict since the U.S. invaded in March 2003. Insurgents have killed more than 1,000 people in the past two months since Iraqi Prime Minister Ibrahim Al-Jaafari took office.

Two new polls reflect American unease about the war. An ABC News-Washington Post poll released yesterday showed that 56 percent of Americans disapprove of Bush's Iraq strategy and almost a quarter say they're ``angry'' about the war. Still, 58 percent say they don't want troops to withdraw before order is restored. A CNN/USA Today/Gallup survey found only 34 percent of Americans think the U.S. and its allies are winning the war.

Combat Readiness

The U.S. says it has trained and equipped 168,500 Iraqi security forces, and plans to have about 275,000 by June 2006. Analysts say those numbers don't reflect how many can effectively replace the U.S. military. There are ``only a handful of units that can operate with some degree of independence,'' Anthony Cordesman, a military analyst at the Center for Strategic and International Security in Washington, told reporters June 24.

The Pentagon says its estimates on the combat readiness of Iraqi forces are classified. Iraqi Foreign Minister Hoshyar Zebari, at the United Nations on May 31, challenged Bush administration assurances of progress in training. U.S. ``numbers and charts'' on Iraqi forces mask continuing problems with leadership and performance, he said. ``It's very important to accelerate the training.''

No Easy Options

Bush has no easy options in Iraq. Leaving before Iraqi troops are capable of taking over could lead to civil war or anarchy, analysts say. Setting a timetable for departure would inspire more attacks by insurgents.

``There are some people who think we can walk away from it and everything will be okay,'' says John Pike, director of Globalsecurity.org, an Alexandria, Virginia-based defense- research group. ``If we were going to walk away from it, it would be Bosnia with oil.''

A new U.S. Central Intelligence Agency assessment says Iraq is now a more potent breeding ground for Islamic terrorists than Afghanistan was in the 1980s. The number of insurgents flowing into Iraq has increased over the last six months and the insurgency's strength is undiminished in that time period, General John Abizaid, commander of U.S. forces in the Middle East told the Senate Armed Services Committee on June 23.

Increasing the number of U.S. troops in Iraq would be politically and militarily implausible given the strains on the military. Experts say it would also fuel Iraqi nationalism. And staying the current course leads to more U.S. deaths.

``Anyone who calls for a timetable is part of the problem and not part of the solution,'' Cordesman says.

Training

Assuming Iraqi security forces are trained on schedule, ``and assuming everything is stable, they would be able to start drawing down by the end of next year, down to half the current numbers by the presidential election'' in 2008, Pike says.

The parallels between Iraq and Vietnam are ``quite strong,'' says Ohio State University Professor John Mueller, a political science professor who has written two books on war and public opinion.

``It's the same thing,'' he says. ``Vietnamization there; here it is Iraqization. The basic idea is you cut and run and set up some kind of government, a political and military system behind you. You give it a certain amount of money and you leave, and that is essentially what happened in Vietnam.''

The number of U.S. casualties now in Iraq is less and the insurgency there isn't state-backed as it was in Vietnam, Mueller notes. ``But the basic idea,'' he says, is ``slogging on until this enemy somehow breaks. We never got there in Vietnam.''

Political Shift

In 1966, as the Vietnam build-up was underway, Democrats lost three seats in the Senate and 47 in the House, though they retained control of both chambers. Today, Republicans hold slimmer majorities, outnumbering Democrats 55 to 44 in the Senate and 231 to 202 in the House.

As public support erodes for keeping American troops in Iraq, Republicans increasingly express fears that mounting casualties will harm them politically next year.

No Republican is calling for an immediate withdrawal, although conservative Republican Representative Walter Jones of North Carolina joined Democrats in calling for troops to start coming home by October 2006.

Senator John McCain, the Arizona Republican, says he senses concern among his Republican colleagues. ``Whenever the polls show indicators that Americans are concerned, it's reflected in their representatives,'' he said in an interview.

`Resolved Isn't Enough'

``What's the only scenario that would make us leave before we should? Public support eroding,'' says South Carolina Republican Senator Lindsey Graham. ``I believe the president is resolved. But being resolved isn't enough. There has to be corrective action.''

Some Republicans are nervous because they ``don't see light at the end of the tunnel,'' Senator Charles Grassley, the Iowa Republican, says. Republicans' angst is so sharp that MoveOn, the political-action committee that campaigned for Democratic presidential candidate John Kerry in 2004, plans to recycle it on television ads starting today.

The ads feature Hagel's charge, from an interview with U.S. News and World Report published June 19, that ``the White House is completely disconnected from reality.'' MoveOn, which has received money from donors such as financier George Soros, plans to spend $500,000 on the TV and print campaign, according to an e- mailed statement yesterday from spokesman Trevor Fitzgibbon.

To contact the reporter on this story: Janine Zacharia in Washington at jzacharia@bloomberg.net