U.S. President Joe Biden says he will lay down "red lines" to Russian President Vladimir Putin in their meeting on Wednesday.

Speaking after a NATO summit of leaders, Biden acknowledged that he faced a tough opponent in Putin.

And he said he was ready to cooperate with Moscow, if it chose to do so, but would respond if Russia continued its harmful activities.

[Clip: Biden]
"I'm gonna make clear to President Putin that there are areas where we can cooperate, if he chooses, and if he chooses not to cooperate and acts in a way that he has in the past relative to cybersecurity and some other activities, then we will respond."