US Defence Secretary Donald Rumsfeld said he respects Japan's decision to delay sending troops to Iraq but the postponement is another sign of the difficulties the US faces in persuading its allies to help in Iraq. With attacks against coalition forces in Iraq increasing, Rumsfeld said he was confident Japan and other nations would make the right decision for themselves. But Rumsfeld also conceded insurgents in Iraq are learning how to stay one step ahead of US forces, adding that the final test would be, "Who's going to outlast the other?" Rumsfeld's comments came as U. forces stepped up its "Operation Iron Hammer" against insurgents and follow a vow from US President George W. Bush that American troops would remain in Iraq until the "job is done."