Harry Reid (D-NV) answers a question here regarding Immigration Reform. Notice the expression - particularly with his mouth - the Senate Majority leader makes at the 0:11 mark. This is a brief and straight-on view of what in body language parlance is known as a "Lip Purse" (see image below).
Pursing of the Lips is a nonverbal that is made by someone who, at least in that moment, perceives himself and his position to be an alpha (relative to the antagonist at hand). It also is a signal that they believe their plan/opinion/answer is superior - however they will only be sharing a part (perhaps none) of it openly. Because they are the relative alpha - they also believe they have a reasonable chance, the resources and power to successfully execute their plan.
Think of the lip purse as a signal of clandestine disagreement and strengthen your "Plan B" for an ambush.
You may not have a master tactician like Senator Reid across the table from you - but you should never take a lip purse casually.
See also:
Nonverbal Communication Analysis # 2391: Jay Carney re: Hillary Clinton and Benghazi - Microexpressions and More
Nonverbal Communication Analysis No. 2439: Michael Jackson's Wrongful Death Suit - AEG Live CEO's Body Language During Deposition
Nonverbal Communication Analysis # 2298: Kylie & Kendall Jenner Do NOT Like Kanye West - Their Body Language Contradicts their Words - Spells another Split-up in Kim Kardashian's Future
Nonverbal Communication Analysis # 2424: Giada De Laurentiis on Conan O'Brien Beautiful Teeth but Insincere Smiles and Some Body Language Signals of Waning Love
Nonverbal Communication Analysis # 2264: Kate Middleton's First Portrait as Duchess of Cambridge Captures Body Language of Contempt, Disapproval and Fatigue
Negotiation Nonverbal Communication Secret # 1151: Xi Jinping's Subtle Pursed Lips
Nonverbal Communication Analysis # 1896: IMF Managing Director - Christine Lagarde Pseudo-Prayer & Pursed Lips
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