Ukraine's military incursion into Russia's Kursk region has "created a real dilemma" for Russian President Vladimir Putin, President Joe Biden said Tuesday, adding that U.S. officials are in constant touch with the Ukrainians about the move.

About 1,000 Ukrainian troops rammed through the Russian border in the early hours of Aug. 6 with tanks and armored vehicles. A U.S. official said late Tuesday that the goal of Ukraine's Kursk incursion appears to be to force Russia to pull troops out of Ukraine to defend Russian territory against the cross-border assault.

Answering questions from reporters upon his arrival in New Orleans, Biden said he has been briefed every four to five hours for the last six to eight days on Ukraine's action.

"It's creating a real dilemma for Putin," he said in his first substantive comments about the operation, which appeared to have caught the Russians off guard.

The U.S. has provided billions of dollars of weaponry to Ukraine intended largely for defensive purposes as Ukraine tries to repel the Russian invasion launched in February 2022.

Biden in May authorized Kyiv to launch U.S.-supplied weapons at military targets inside Russia that are supporting an offensive against the northeastern Ukrainian city of Kharkiv.

The White House said Ukraine did not provide advance notice of its incursion. Russian forces Tuesday retaliated against Ukrainian troops with missiles, drones and airstrikes.

White House press secretary Karine Jean-Pierre told reporters on board Air Force One that the Biden administration was not involved in the operation.

"We had nothing to do with this," she said. "We have no involvement. We'll continue to have conversations with the Ukrainians about their approach, but it is really for them to speak to."

Putin has said he believed Ukraine's operation was aimed at improving Kyiv's negotiating position ahead of possible talks and slowing the advance of Russian forces along the front.

U.S. officials said the objectives of Ukrainian President Volodymyr Zelenskyy remain to be seen.

"We're trying to figure out exactly what they are doing and the goal here, and it's still not 100% clear," a U.S. official told Reuters.