WASHINGTON — President Barack Obama is expected — as early as today — to ask Congress for new war powers, sending Capitol Hill his blueprint for an updated authorization for the use of military force to fight the Islamic State group.

Haggling then begins on writing a new authorization to battle the Sunni extremists, who have seized territory in Iraq and neighboring Syria and imposed a violent form of Sharia law.

That will lead to the first war vote in Congress in 13 years — one of the most important votes faced by members of the House and Senate.

To get Congress to approve his request, Obama must find a balance between lawmakers who want wide authority to fight the Islamic State group and others, including members of his own party, who worry that a new authorization to use military force will lead to U.S. entanglement in another protracted war.

In 2002, Congress passed a resolution authorizing President George W. Bush to use force against Iraq — a vote that scores of Democrats have regretted and then-candidate Barack Obama used as a cudgel against his rivals to win the Democratic presidential nomination.

Obama so far has relied on congressional authorizations that former President Bush used to justify military action after 9-11. Critics say the White House’s use of these authorizations to fight the terrorist group is a legal stretch at best. The president earlier insisted he had the legal authority to deploy more than 2,700 U.S. troops in Iraq to train and assist Iraqi security forces, and conduct ongoing airstrikes against targets in Iraq and Syria. More recently, the president has said he wants a new authorization, but has not released details.