Gen. David Petraeus, the top U.S. military commander in Iraq, is due to assess on Monday whether President Bush's move to add 30,000 troops in Iraq this year has succeeded - and what troop levels are needed going forward.

Besides Petraeus, U.S. Ambassador to Iraq, Ryan Crocker, is also expected to argue before the US Congress that a major pullout of U.S. forces would hurt progress made since troop numbers were increased by 30,000 earlier this year.

Both Petraeus and Crocker will speak before a joint session of the House Armed Services and Foreign Relations Committees.

According to media reports, Petraeus had earlier recommended that decisions on major troop cuts in Iraq be delayed until March 2008.

Petraeus wrote in a letter to troops last week that sending 30,000 more troops into the war zone in January had failed to yield the desired reconciliation among Iraqis.

It has not worked out as we had hoped, the general had said, adding that the situation in Iraq is exceedingly complex and that progress had been uneven.

When Petraeus took up his command in February, the central rationale for the surge was that the deployment of an additional 30,000 US troops would give breathing space to the government of Nuri al-Maliki to draft legislation and embark on political reconciliation.

In his letter to the troops serving in Iraq, which was obtained by the Washington Post, the general acknowledged that had not occurred. Many of us had hoped this summer would be a time of tangible political progress at the national level, Petraeus wrote. All participants, Iraqi and coalition alike, are dissatisfied by the halting progress on major legislative initiatives, he said.

The expressions of disappointment were a departure for Petraeus, who has been forceful in conveying what he sees are the success stories of the Bush administration's strategy in Iraq.

He continued to emphasize there had been isolated gains in Iraq, including what he called local reconciliation, in the isolated pockets where tribal leaders had formed alliances against Al-Qaeda.

The general also paid tribute to the strains the long and repeated deployments are putting on US forces. We have to contend with the relentless pace of operations, the crushing heat, and the emotions that we all experience during long deployments and tough combat, he wrote.

Few of these political solutions would have been possible without the improved security provided by coalition and Iraqi forces, the Globe had quoted Petraeus as saying.

Media reports have also suggested that Petraeus might recommend a symbolic withdrawal of just one brigade, about 3,500 to 4,000 troops, early next year to appease Bush critics. The process will take time, but we want to be sure to maintain the security gains that coalition and Iraqi forces have worked so hard to achieve, the Globe had quoted the general as saying. In a number of recent interviews, Petraeus also indicated that he does not foresee replacing the troops deployed in the surge when their tours of duty in Iraq come to an end in April 2008.

Though political observers agree that the increase in US troops may have created some tactical military gains - especially in Baghdad and Anbar province, yet, they are well aware that political reconciliation between Iraq's various ethnic groups is yet to see any progress.

In a BBC World Service poll of 23 000 people in 22 countries, 67 percent said they backed a US troop withdrawal inside a year, while fewer than half (49 percent) believed the United States would permanently leave troops in the country.