Meanwhile, Maria Sharapova beat Ekaterina Makarova in straight sets.
World No 7 Johanna Konta has reached the second round of the Porsche Grand Prix in Stuttgart, beating Japan's Naomi Osaka 7-6 (7-5) 3-6 6-1, to put a hard weekend behind her.
Asked by the media about the comments, Sharapova said: "I don't have anything to say - I am way above that".
Both women held serve comfortably throughout most of the first set, with the first sign of alarm coming when Sharapova trailed 0-30 at 4-4.
A missed forehand opportunity then cost Konta as she was broken in the 11th game and Sevastova served out the victory with her sixth ace.
U.S. to employ mix of sanctions, diplomacy to rein in North Korea
The officials weren't authorized to speak publicly about plans for the closed-door briefings and requested anonymity. According to Yonhap news agency, the parts include two or three launchers, intercept missiles and a radar.
Konta initially struggled for consistency against her Japanese opponent on Wednesday afternoon, with the first set being taken to a decider before Osaka clinched the second set.
Sharapova, who had tested positive at the 2016 Australian Open, picked up where she had left off against Vinci, to power through and set up a clash against Estonian qualifier Anett Kontaveit.
The world number seven broke in the opening game but failed to hold her own serve until her fourth attempt. "I felt like I settled down a little bit and was able to focus on the game". I executed a great plan.
"Practicing is so different to matches, you can not compare it". It's great to come out and play matches.
Sharapova received a wild card for the tournament after having lost all her ranking points in the wake of her suspension.
Comments