On the eve of the anniversary of September 11 deadly terror strikes on the US,President Barack Obama said American forces were in pursuit of al-Qaeda leader Osama bin Laden and his deputy who had been forced to go deep underground. Pressure is on in the Af-Pak region to hunt down the worlds most wanted terrorist,Obama said as he warned Americans to be prepared to face terror threat from other al-Qaeda cadres. One of the things that weve been very successful at over the last two years is to ramp up the pressure on al-Qaeda, Obama said. As a consequence,they have been holed up in ways that have made it harder for them to operate. And part of whats happened is. bin Laden has gone deep underground. Even Zawahiri,who is more often out there,has been much more cautious, Obama said.