GENEVA (AP) — The Swiss government is hoping to rid itself of a long-running headache over banking secrecy tomorrow when lawmakers are expected to approve a treaty to hand files on thousands of suspected tax cheats to US authorities.

A stand-off among lawmakers, courts and the government has held up ratification of the deal that Swiss and US authorities signed in August to lift the threat of US prosecution from Switzerland's largest bank, UBS AG.

The hoped-for resolution may yet be stalled as members of the nationalist Swiss People's Party and the left-of-centre Social Democrats demand concessions in return for their consent. The debate in Switzerland's lower house — or National Council — starts today.

If the option favoured by government and centrist parties is passed it would spell the end of UBS's three-year battle with US tax authorities that culminated in revelations the bank had for years helped American clients hide millions of dollars in offshore accounts. The deal is crucial to UBS, which has faced intense pressure from US authorities since 2007. Last year the bank agreed to turn over hundreds of client files and pay a $780 million penalty in return for a deferred prosecution agreement.