"Throughout [Brexit negotiations], we must maintain the strength and unity of the transatlantic community and alliance," Lew stated. "That is why we are committed to continuing to work together on the Transatlantic Trade and Investment Partnership to enhance trade, job creation and growth."
In June, EU Trade Commissioner Cecilia Malmstrom stated that Great Britain will continue to be included in TTIP negotiations despite its decision to leave the European Union.
Lew on Tuesday stressed that the UK, EU and US relationships should remain strong despite the British decision to leave the 27-member bloc.
The TTIP free trade agreement, negotiated since 2013, involves the creation of a free trade zone between Europe and the United States. Canada, Mexico, Switzerland, Liechtenstein, Norway and Iceland will also participate in the TTIP deal.