WASHINGTON — The Pentagon will send Ukraine at least $275 million in new weapons, U.S. officials said Tuesday, as the Biden administration rushes to do as much as it can to help Kyiv fight back against Russia in the remaining two months before President-elect Donald Trump takes office.

The latest tranche of weapons comes as worries grow about an escalation in the conflict, with both sides pushing to gain any advantage that they can exploit if Trump demands a quick end to the war — as he has vowed to do.

In rapid succession this week, President Joe Biden gave Ukraine the authority to fire longer-range missiles deeper into Russia and then Russian President Vladimir Putin formally lowered the threshold for using nuclear weapons.

U.S. officials contend that Russia’s change in nuclear doctrine was expected, but Moscow is warning that Ukraine's new use of the Army Tactical Missile System, known as ATACMS, inside Russia on Tuesday could trigger a strong response.

One American official said the U.S. is seeing no indications that Russia is preparing to use a nuclear weapon in Ukraine. The U.S. officials spoke on condition of anonymity because the aid package has not yet been made public.

Asked Tuesday if a Ukrainian attack with longer-range U.S. missiles could potentially trigger use of nuclear weapons, Kremlin spokesman Dmitry Peskov answered affirmatively. He pointed to the doctrine’s provision that holds the door open for it after a conventional strike that raises critical threats for the “sovereignty and territorial integrity” of Russia and its ally Belarus.

A U.S. official said Ukraine fired about eight ATACM missiles into Russia on Tuesday, and just two were intercepted. The official said the U.S. is still assessing the damage but that the missiles struck an ammunition supply location in Karachev, in the Bryansk region.

The weapons in the new package of aid for Ukraine include an infusion of air defense, including High Mobility Artillery Rocket Systems (HIMARS), as well as 155 mm and 105 mm artillery rounds, Javelin anti-armor munitions and other equipment and spare parts, U.S. officials say.

The weapons will be provided through presidential drawdown authority, which allows the Pentagon quickly to pull supplies from its shelves to speed them to Ukraine’s front line.