WASHINGTON, Aug. 9 (Xinhuanet) -- Given the increasing violence inIraq, no one knows for sure when US troops could start a major pullout, two senior officials admitted Tuesday.

    The accurate time of a large-scale withdrawal depends on Iraq'spolitical progress, the security situation in the country and the capability of the newly-founded Iraqi forces, both Chairman of theJoint Chiefs of Staff Gen. Richard Myers and Secretary of Defense Donald H. Rumsfeld told a news briefing at the Pentagon.

    When asked about when Iraqi forces can take the lead in fighting militants, Myers replied, "nobody knows."

    He described the issue as "event-driven" and it is going to be "driven by a lot of events."

    The US military will wait until events on the ground could givea clear answer, said Myers.

    Rumsfeld also offered no new thoughts on the pullout plan, saying any decision on the issue will be based on commanders' understanding of the security situation and the capabilities of the now 173,000-strong Iraqi security forces.

    Earlier, Pentagon officials said they were considering a plan to gradually withdraw US forces from Iraq next year.

    However, a Pentagon spokesman announced Monday that it is highly likely for the US military to temporarily raise the troop levels in Iraq, so as to enhance security during the country's October constitutional referendum and December's elections.

    Local analysts pointed out that while the Pentagon envisions pulling some of the US troops out of Iraq next year once the situation is stabilized, the increasing violence has made a short-term reinforcement more urgent. Enditem