One of the bloodiest single days for US troops in the conflict brought the total of US soldiers killed to 21 in western Iraq since Monday, and the US death toll since the March 2003 invasion to 1,811.

Gunmen meanwhile murdered a US freelance reporter in southern Iraq, and insurgents claimed they had captured another US Marine.

"The violence in recent days in Iraq is a grim reminder of the enemies we face," Bush said after travelling to the town of Grapevine, Texas, on the first full day of his month-long working vacation.

Latest developments were somewhat overshadowed in the US media, fixated on dramatic spacewalks from the Shuttle Discovery and the miraculous escape of more than 300 people in a fiery Air France crash in Toronto.

But the fact that the admired and talismanic US Marines were caught in the crosshairs could weigh on public opinion, after recent polls showed increasing disquiet among Americans at the cost of the Iraq war.

While Bush is in Texas, his political advisors will be plotting short-term political implications, also mindful that crucial mid-term Congressional elections in 2006 are on the horizon.

They must also square their aspirations with a US government audit last week that security woes were slowing progress in Iraq deemed vital to stilling the insurgency.

And rising violence calls into question Vice President Dick Cheney's remark in May that the insurgency was in its "last throes."

Eighty-two percent of people polled by Foreign Affairs and Public Agenda for a survey released Wednesday, but conducted before the latest spike in violence, worried a lot, or somewhat that the Iraq war was reaping too many casualties.

"The picture we have is really quite similar to that of a lot of polls that share a growing concern about the situation in Iraq," said Public Agenda Chairman Daniel Yankelovich.

"The concern is growing. There is no question."

A July 21 poll by Pew Research Center for People and the Press, found only 27 percent of people said Bush had a clear plan to bring the Iraq venture to a successful conclusion -- the lowest such percentage since the start of the war.

In late June, an ABC News/Washington Post poll found 57 percent of Americans believed that Bush had "intentionally misled" them to wage war in Iraq.

Bush on Wednesday insisted he would not lay down a timetable for the withdrawal of US troops.

"I hear all the time, 'Well, when are bringing the troops home?' And my answer to you: 'As soon as possible but not before the mission is complete,'" Bush said.

But while Bush insists he will not desert Iraq, other senior US officials, mindful of sagging public approval, are talking openly about a drawdown of troops.

"Once Iraq is safely in the hands of the Iraqi people, and a government they elected under a new constitution, our troops will be able to come home with the honor they have earned," Secretary of Defence Donald Rumsfeld said in prepared remarks for a speech in Dallas, Texas, Tuesday.

Newsweek reported Sunday that Washington plans to reduce troop levels to 80,000 by mid next year and to 60,000 by the end of 2006.

Fewer US troops on the ground is likely to mean fewer casualties -- and less of an incendiary presence for insurgents.

Politically, a partial US withdrawal would allow Bush to point to progress in Iraq ahead of the 2006 elections.

In a worrying sign for the White House, a US congressional race decided Tuesday and seen as an early barometer for those polls, turned on the question of Iraq as Marine reservist and Iraq veteran Paul Hackett was only narrowly defeated by his Republican opponent in a highly conservative Ohio district.

The key to any drawdown of US troops lies in the readiness of Iraqi troops -- and their ability to fight insurgents or radical Islamic groups -- an issue which has been frequent bone of contention between Bush and his opponents.

"We are never going to win this thing militarily, that is the bottom line,"

said Lieutenant General John Sattler of the First Marine Expeditionary Force, in a candid conversation in Washington last week.

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