Unclear how bomber got close to Cheney base-W House

WASHINGTON, Feb 27 (Reuters) It is unclear how a suicide bomber was able to get close to a US base in Afghanistan where Vice President Dick Cheney was staying, the White House said today.

''At this point, people are still investigating what happened, so we don't have a firm answer for you,'' White House spokesman Tony Snow told reporters.

Up to 14 people were killed, including one American and one South Korean soldier, in an attack on the Bagram base rebels said was aimed at Cheney. A US official said Cheney was about half a mile (1 km) away on the base and never in danger.

Snow called it an ''isolated attack'' and declined to say whether it was a sign of Taliban strength.

''We've often said about acts of terror: An individual who wants to commit an act of violence or kill him or herself -- very difficult to stop. But I'm not sure that you can draw larger conclusions about any organisation based on an incident such as this,'' Snow said.

President George W Bush's initial reaction to the attack was concern about whether Cheney was all right, he said.

The US vice president is expected to meet Bush tomorrow after his return from a trip that included last-minute stops in Afghanistan and Pakistan.

His visit was aimed in part at voicing concerns to Pakistani President Pervez Musharraf and Afghan President Hamid Karzai about the threat from al Qaeda and its Taliban allies on the Afghan and Pakistani borders, with a spring offensive from the Taliban expected in the spring.

REUTERS SBA RN0137