Top members of the Bush administration have been speaking out to try to convince US public opinion that success can be achieved in Iraq.
The US wants Iraqi security forces to take charge of security duties
Defence Secretary Donald Rumsfeld was among several officials defending the government's Iraq policy as adaptable, as US mid-term elections approach.
The US envoy to Iraq earlier said Iraq could be stabilised, despite setbacks.
A top Republican has meanwhile joined Democrats in criticising Mr Bush in a month of high US casualties.
More than 90 US servicemen have died in Iraq, the highest toll since November 2004.
Three hundred Iraqi troops have also died in October, and some estimates say sectarian attacks now claim an average of 40 Iraqi lives every day.
According to the BBC's Justin Webb in Washington, the Bush administration is trying its best to suggest it has a plan to end the violence.
On Tuesday, the US ambassador and military commander in Baghdad told US viewers via a rare televised joint news conference that success in Iraq was still possible.
Ambassador Zalmay Khalilzad said there would be setbacks, but the aim of creating a multi-ethnic and multi-faith Iraq remained unchanged.
Gen George Casey said Iraqi forces should be able to assume responsibility for security in the next 12 to 18 months, with minimal aid from the US.
Iraq's National Security Adviser Mowaffaq al-Rubaie subsequently confirmed that the Iraqi government had accepted the proposed measures.
"We have agreed on a timeline. Remember, we have achieved a great deal over the past three years," he told CNN.
But a note of caution was sounded by a senior Iraqi politician, Adnan Pachachi, who told the BBC he doubted that the Iraqi police would be ready to take control so quickly.
"First they have been heavily infiltrated by the militias they are supposed to fight. Secondly, I think they have been deprived of the necessary equipment and weapons. They lack the motivation to fight. They lack discipline," Mr Pachachi said.
Mr Pachachi also warned of chaos if coalition forces withdrew from Iraq too quickly.
Change in tactics
Several top administration officials discussed Iraq with a gathering of conservative talk radio hosts at the White House on Tuesday.
Defence Secretary Donald Rumsfeld was asked why President Bush appeared to have abandoned the Republicans' recent slogan that the party was planning to "stay the course" in Iraq.
"I suppose the concern was that it gave the opponents a chance to say, 'well, he's not willing to make adjustments' - and of course just the opposite is true," Mr Rumsfeld said.
President Bush echoed this view in an interview with CNBC TV, saying he had been "talking about a change in tactics... ever since we went in".
National Security Adviser Stephen Hadley meanwhile said the violence in Iraq is unlikely to end during Mr Bush's presidency.
"Is there going to be peace? Is there going to [be] the end of any violence? Of course not. This violence is going to go on for a long time," Mr Hadley said.
But, he added, the US hoped Iraqi institutions would eventually be able to contain the threats to the country's security.
'Verge of chaos'
Our correspondent says the Republican party is hoping that Tuesday's efforts to defend policy in Iraq will convince the party's supporters that all is not lost there, before mid-term polls in two weeks' time.
An opinion poll conducted during the last few days for CNN suggests that only 20% of Americans think the war is being won. The figure was 40% a year ago.
A top Republican Senator decided to speak out on Tuesday, arguing that the White House has lost its direction in Iraq.
"We're on the verge of chaos and the current plan is not working," Senator Lindsey Graham said.
He said Mr Rumsfeld and the US military commanders in Iraq must "come up with a game plan" to end the fighting.