In recent days several senior Republicans, such as Indiana senator Richard Lugar, have broken ranks with the president over Iraq.
An interim report on the progress of the troop surge is due out later this week and is expected to show only mixed results triggering further debate over Bush's strategy.
Speaking in Ohio however, Bush said the troops would stay and called on critics to wait for a report due in September from General David Petraeus, the US commander in Iraq.
Call to wait
"I believe Congress ought to wait for General Petraeus to come back and give his assessment of the strategy that he's putting in place before they make any decisions," he said.
|Bush is facing growing pressure for a rethink |
from members of his own party [EPA]
"That's what the American people expect… And that's the way I'm going to play it as commander in chief."
Al Jazeera's Washington correspondent Rob Reynolds says Bush spoke as though his faith in a desirable outcome in Iraq would make victory happen.
"I strongly believe democracy will trump totalitarianism every time," the US president said.
"That's what I believe, and those are the belief systems on which I am making decisions."
He said the US troop presence in Iraq was necessary "for the security of the United States and the peace of the world".
"I strongly believe it, and I strongly believe we'll prevail," he said.
But the president's faith does not appear to be reflected among American voters.
'Tide has turned'
According to a USA Today/Gallup poll released on Tuesday more than seven in 10 Americans favour withdrawing nearly all US troops from Iraq by April.
The same poll showed 62 per cent thought sending US troops to Iraq was a mistake - the first time that number has topped 60 per cent in that poll.
Acknowledging the public mood, Republican Senator Olympia Snowe said impatience for a shift in policy was continuing to grow and that by September there could be enough support among Democrats and disaffected Republicans to pass a withdrawal timetable.
"The tide has turned," Snowe said.
Adding to pressure on Bush from within his own party, John Warner, a Republican senator from Virginia, told reporters he was working with other disaffected Republicans on a proposal about Iraq that is in the "formative stages."