The President is the only one authorized by Section 337 to take this action. Although the President assigned his authority to the trade representative on his behalf, this action is only permitted under the law to the extent it is done by the President.

Here's the law, 19 U.S.C. § 1337 (http://www.law.cornell.edu/uscode/text/19/1337):

"(j) Referral to President

(1) If the Commission determines that there is a violation of this section, or that, for purposes of subsection (e) of this section, there is reason to believe that there is such a violation, it shall—

[...]

(B) transmit to the President a copy of such determination and the action taken.... If, before the close of the 60-day period beginning on the day after the day on which he receives a copy of such determination, the President, for policy reasons, disapproves such determination and notifies the Commission of his disapproval, then, effective on the date of such notice, such determination and the action taken under subsection (d), (e), (f), (g), or (i) of this section with respect thereto shall have no force or effect."