President Biden has approved the deployment of another Patriot missile system to Ukraine, senior administration and military officials said, as the country struggles to fend off Russian attacks on its cities, infrastructure and electrical grid.

Mr. Biden’s decision came last week, the officials said, after a series of high-level meetings and an internal debate over how to meet Ukraine’s pressing needs for bolstered air defenses without jeopardizing U.S. combat readiness.

The new Patriot system — the second that the United States has sent to Ukraine — will come from Poland, where it has been protecting a rotational force of American troops who will be returning to the United States, officials said.

The system could be deployed to Ukraine’s front lines in the next several days, U.S. officials said, depending on any maintenance or modifications it needs.

Considered one of the United States’ best air-defense weapons, the Patriot includes a powerful radar system and mobile launchers that fire missiles at incoming projectiles.

It is also one of the scarcest weapons systems in the U.S. arsenal. Pentagon officials refuse to disclose how many it has, but one senior military official said that the Army has deployed only 14 of them, in the United States and around the world. American allies also have Patriots, and two of those nations have sent a couple to Ukraine, but U.S. officials say they hope European powers will send more.