Can the president force Congress to convene?

Yes. Among the power of the president, Article 2, Section 3 states that the president ". . .may, on extraordinary occasions, convene both Houses, or either of them . . ."

In his Commentaries on the Constitution of the United States, Justice Joseph Story explained "extraordinary occasions" as including the need "to repel foreign aggressions, depredations, and direct hostilities; to provide adequate means to mitigate, or overcome unexpected calamities; to suppress insurrections; and to provide for innumerable other important exigencies, arising out of the intercourse and revolutions among nations."