WASHINGTON — Congress returns to work facing a momentous vote on whether the United States should attack Syria, a question that overshadows a crowded fall agenda.

Lawmakers come back Monday after a five-week break.

Many in Congress stand as a major obstacle to President Barack Obama’s promised strikes against Syria.

Obama insists the world must act. He blames Syrian President Bashar Assad for gassing his own people, killing 1,429 civilians, including 426 children. The Syrian government has denied responsibility.

Even before Syria, Congress faced a difficult fall ith fights over a stop-gap spending bill and an increase in the government’s debt limit to avert a market-rattling default.

A farm bill, a defense policy measure and potential limits on government surveillance programs remain unfinished.