UBS, Switzerland's biggest bank, has proposed an increased dividend and new share buyback programme despite a hefty writedown from a tax overhaul in the US. 

The bank posted a 2.2 billion Swiss franc ($2.3 billion) net loss for the fourth quarter of 2017 as the US tax reforms saddled it with a 2.9 billion franc writedown. Pre-tax earnings rose 34%. 

The bank also lowered capital targets up to 2020 and decoupled its shareholder payout policy from a previous capital ratio floor.

This is ahead of an anticipated drag on its finances from new international rules known as Basel III. 

"Greater regulatory clarity means we can open a new chapter for UBS, allowing us to sharpen our focus on growth across our businesses, make further investments in technology and deliver attractive returns to shareholders," chief executive Sergio Ermotti said in a statement. 

The bank proposed an increased dividend of 0.65 francs per share, matching analysts' expectation for a dividend hike from 0.60 francs the year before. 

The bank also said it was launching a three-year share buyback programme of up to 2 billion francs, to begin in March. 

Announcing it would be combining Wealth Management Americas and Wealth Management into one unified Global Wealth Management division, the bank set targets for 2-4% net new money growth per year.