"Having passed the House on Tuesday 419-3, the sanctions bill now goes to President Donald Trump, who has expressed a reluctance to sign the measure. That’s likely because lawmakers wisely inserted a provision in the bill requiring the president to talk to Congress before rolling back any sanctions."

If he vetos this bill we know that he is in bed with the Russians (as if it is not already obvious).  Perhaps worried about the Pee pee tape?  Seriously though, since his veto could be overridden he is better off signing since 1) He will appear not to be controlled by Putin, and 2) It is embarrassing to have your veto overridden and Trump hates to look bad.