BofA said the dollar had risen since the US Federal Reserve's December meeting despite narrowing spreads against most other global currencies, which could be a "red flag" for bulls at a time when sentiment is one-sided. "The dollar remains supported despite the inverse spread," BofA FX strategists Alex Cohen, Adarsh Sinha and Janice Xue wrote in a note on Tuesday. "Congested positions and increasingly consistent FX sentiment expose asymmetric risks."