WASHINGTON (Reuters) - The United States is working around the clock to provide Ukraine with supplies to defend itself against an intensified Russian attack that could target Kharkiv, the White House said on Friday.

Russian forces launched an armored ground attack on Friday near Ukraine's second largest city of Kharkiv in the northeast of the country and made small inroads, opening a new front in a war that has long been waged in the east and south.

"It is certainly possible that the Russians are setting themselves up for a larger assault on Kharkiv," White House national security spokesperson John Kirby told reporters. He said it was concerning signs that Russia appears to be preparing to use long-range fire within range of Kharkiv.

"You're not going to do that if you're not also thinking about some other larger assault directly on the city," Kirby said.

The United States is preparing a $400 million military aid package for Ukraine, as the U.S. returns to a regular pace of supplying weapons to Kyiv after lawmakers passed a $95 billion bill, the White House said on Friday.

The Ukraine aid package includes artillery, munitions for NASAMS air defenses, anti-tank munitions, armored vehicles and small arms that can immediately be put to use on the battlefield, a U.S. official told Reuters.

The weapons aid will utilize Presidential Drawdown Authority, or PDA, which authorizes the president to transfer articles and services from U.S. stocks without specific congressional approval during an emergency. As a part of the $95 billion aid bills, Congress authorized $60.8 billion worth of various forms of aid to Ukraine, including $8 billion worth of PDA items.

(Reporting by Steve Holland, Doina Chiacu, Katharine Jackson; Editing by Doina Chiacu)

By Steve Holland and Katharine Jackson