.SAN JUAN, Puerto Rico (AP) – Thousands of Puerto Rican teachers marched to the gates of the governor’s mansion Sunday, threatening to go on strike for higher salaries and better working conditions if long-stalled bargaining talks are not resumed.

The two sides will sit down again Monday to try to resolve the two-year impasse. But union leaders representing the majority of Puerto Rico’s 42,000 public school teachers plan a Tuesday news conference to announce a strike date if no agreement is reached.

“We hope to send a firm message to Gov. Aníbal Acevedo Vilá so that the agreement is signed,” Teachers Federation President Rafael Feliciano said among a throng of marchers.

The island’s department of education and the union have agreed to 26 articles of a proposed collective-bargaining agreement, but 20 others remain unsigned, including 16 salary-related clauses.

The looming strike has divided the union’s roughly 32,000 members as some urge restraint, saying the group’s first strike since 1993 should be a last resort. Strikers could be fired under a local law that forbids disruption of the public education system.

The starting salary for a teacher in the U.S. territory is $19,200 a year – about a third less than the average public school teacher salary on the U.S. mainland.