UBS has lifted its rating for the global banking sector from 'underweight' to 'overweight', saying that the operating environment is beginning to improve.In a research report titled 'Post-crisis banking', UBS said that the tone of its Global FID conference earlier this week was "neutral to slightly positive" and banks are starting to see "improving bottom-up trends".The broker had a cautious stance in early February after the sharp rally since mid-2012 left banks over-bought in the midst of a challenging political landscape (Italy, Cyprus, US budget talks) and slowing economic momentum. Many of these obstacles have now been absorbed, analysts said.UBS said that credit demand has started to pick up in the States - despite low rates continuing to weigh on margins - and capital markets got off to a good start in the second quarter. Meanwhile, banks are still looking to reduce costs while capital ratios look on track to hit Basel III requirements."Post our global financials conference, our global equity strategy team has upgraded global financials [...] on the basis that the global economy is healing, capital has been rebuilt and the sector has moved from being a net issuer to net distributor of cash."From a regional perspective, the broker now has an 'overweight' position in the US banking sector given attractive valuations, strong balance sheets and a hopefully recovery in the housing market. Europe has been upgraded to 'neutral' and UBS has a preference for Nordic and UK banks. Canada and Japan however have been downgraded to 'neutral'.The banking sector in London was making a collective gain of 1.02% in morning trade on Friday.BC