Trump says he will veto any legislation Congress sends to his desk that weakens the protection of human life.
Trump, speaking to reporters at the White House before flying to California, also reiterated that he had been told the crown prince had not played a role in the journalist's death.
Trump has not openly suggested dropping Pence from the ticket with the 2020 presidential election rapidly approaching.
Asean, which will hold its own summit on Tuesday before being joined by other leaders, also faces the challenge of working through sharp differences over the handling of the Rohingya minority by Myanmar.
Pence assailed China as a military aggressor, a prolific thief of US technology and, controversially, as interfering in American elections.
White House spokeswoman Sarah Sanders said Trump asked Pence to represent him at the summits.
Pence met Thursday with leaders from the three Central American nations, which the administration has criticized for not doing enough to stem the flow of people trying to enter the US illegally.
Pence met with Ecuadorean President Lenin Moreno as part of a tour of Latin America that has included meetings with Venezuelans who left the socialist country because it is so difficult to obtain food or medicine.
After a May 20 election which Washington rejected as a "sham," US President Donald Trump tightened pre-existing sanctions against Maduro's regime.
British Foreign Secretary Boris Johnson is travelling to the United States on Sunday for a two-day visit, during which he will meet Vice President Mike Pence and national security adviser John Bolton, Britain said.
US Vice President Mike Pence blasted "weak" and "ineffective" immigration laws Monday during a trip to the border with Mexico, as a caravan of immigrants two hours to the west prepared to claim asylum in America.