Unlike past appearances at worldwide summits, the vice president had to dive into the packed agenda on short notice.
The summit in Peru is a once-every-three-years meeting of leaders from across Latin America, the U.S. and Canada.
Trump and Pena Nieto have yet to meet in person since Trump became president past year.
Dozens of pro-Castro supporters were also present in Lima and on Thursday raucously interrupted a meeting to protest what they consider Cuba's mistreatment by the Washington-based Organization of American States.
The United States, France and Britain have been moving warships and aircrafts close to Syria in recent days, fuelling speculation that military action could be imminent.More news: Stockton's lone air carrier Allegiant Air under fire after 60 Minutes report
Senate Democrats are urging Vice President Mike Pence to use his trip to Lima to reset relations with a region where they say President Donald Trump's immigrant-bashing rhetoric is costing the USA influence.
Under former U.S. President Barack Obama, the TPP had been pitched as a way to secure an edge over China in a fast-growing region that includes large swaths of Latin America. Vizcarra himself only recently took power after former President Pedro Pablo Kuczynski resign following revelations he'd failed to disclose payments to his private consulting company from Odebrecht, the Brazilian construction giant at the center of Latin America's biggest graft scandal.
Vice President Mike Pence says the US will provide almost $16 million in humanitarian aid for Venezuelans who have fled their country during the political crisis under President Nicolas Maduro.
Business leaders are set to convene the first meeting of the summit on Monday morning.
"I think President Pena Nieto understands that he and President Trump have a difference of opinion on that", Pence said.More news: Trump strikes deal with top Senate Republican to protect legalized marijuana states
The declaration expressing concern over the "aggravation of the crisis" was signed by Argentina, the Bahamas, Brazil, Canada, Chile, Colombia, Costa Rica, Guatemala, Guyana, Honduras, Mexico, Panama, Paraguay, Peru, Saint Lucia and the United States.
"Canada stands with our friends in this necessary response, and we condemn in the strongest possible terms the use of chemical weapons in last week's attack", Canadian Prime Minister Justin Trudeau told the gathering of regional leaders.
Pence, who is representing the United States at the Summit of the Americas in place of President Donald Trump, said he hoped that the military action, which also involved France and Great Britain, would cause Syria "and their patrons in Russian Federation and Iran" to abandon "the use of chemical weapons against innocent civilians". The Trump administration has been trying to rally support in Latin America to further isolate President Nicolas Maduro's regime and press for stricter penalties for Maduro's deepening authoritarian grip on power.
Mexico also is taking part in a renegotiation of the North American Free Trade Agreement with the US and Canada due to demands for changes from Trump.
The deal was meant to create a sweeping trade bloc and help counterbalance China's economic influence. He learned only Tuesday he would be attending in Trump's place therefore that the president would afford the US response to Syria.More news: Gmail is testing sending confidential emails that automatically expire
In a series of meetings with Latin American leaders, Pence plans to promote good governance and democratic institutions and urge allies to maintain pressure on Maduro.