The U.S. currency teetered near a two-month low against the Australian dollar and a two-year low against the New Zealand dollar, both considered barometers of risk sentiment due to their close ties with the global commodities trade. The U.S. dollar's declines are likely to continue because a vaccine and the expected choice of former Federal Reserve Chair Janet Yellen as U.S. President-elect Joe Biden's next Treasury secretary relieve two big uncertainties for investors. Research suggesting that a COVID-19 vaccine could be available before year end has sent U.S. stocks surging to record highs and reduced the appeal of holding the dollar as a safe-harbour currency. Risk appetite has also improved after the outgoing U.S. President Donald Trump's administration began cooperating with the Biden transition, and after reports that Yellen, an advocate of more fiscal spending, will take the top job at Treasury.