* Justice Breyer to retire, giving Biden a choice for shaping Supreme Court
* Federal Reserve hints at possibility of several interest rate hikes this year
* US formally rejects Russian demand to bar Ukraine from NATO
* Russia and Ukraine will continue ceasefire talks
* N. Korea continues ballistic missile tests–its sixth round of launches this month
* Will Taiwan’s key role in producing computer chips trigger US-China conflict?
* UBS agrees to buy robo adviser Wealthfront for $1.4 billion
* New US home sales rose to a 9-month high in December: