UPDATE 1-Basel Committee adopts tighter trading book rules

(Adds more detail)

BASEL, Switzerland, July 13 (Reuters) - The Basel Committee has adopted the final version of its new rules that will force banks to tie up more capital to offset risky trading book activities with more changes on the way.

The Basel Committee on Banking Supervision, made up of central banks and banking supervisors from across the world, is reforming its Basel II rules, a framework used globally by banks to calculate how much capital they should set aside in case assets tumble in value as they did in the financial crisis.

Basel II was widely seen as failing to ensure banks had a big enough capital buffer to withstand the credit crunch and avert bailouts by governments.

The changes announced on Monday will also require more capital on re-securitised products and better disclosure of securitised assets.

"These additional disclosure requirements will help reduce market uncertainties about the strength of banks' balance sheets related to capital market activities," the committee said in a statement.

The committee will come out with more guidance before the end of the year on how to turn the changes to trading book capital into hard percentage figures for banks to apply.

The changes should be implemented no later than 31 Dec. 2010 while new supervisory guidelines will be introduced immediately.

Assets parked on the trading book had needed less offsetting capital than if they were on a bank's balance sheet, a loophole policymakers were keen to close as soon as possible.