HOUSTON — President Trump faces a difficult juggling act as he tries to persuade China, India and other countries to join in oil sanctions against Iran while also pressuring Venezuela.

Since the two oil-producing giants compete for the same markets, squeezing one may end up helping the other. Squeezing both may send oil prices soaring.

A Venezuelan election is scheduled on Sunday that President Nicolás Maduro is almost certain to win because the main opposition is boycotting the vote, calling it a sham. To protest election abuses and human rights violations, Trump administration officials have warned that Venezuela could face tighter financial sanctions, including measures making it harder to export oil.

The administration is also working to reduce Iran’s oil exports now that it has removed the United States from the nuclear deal negotiated by the Obama administration. Unless Iran and the other countries that signed the 2015 nuclear pact can reach a compromise, Washington plans in the coming months to press a number of punishing measures, like sanctions on banks in countries that do not reduce Iranian oil imports.