"We have to re-examine the value of NATO and that alliance for our country," Rubio said in an interview with Fox News on Tuesday.
Rubio also accused NATO of acting unilaterally against the United States amid the refusal of several allies to assist Washington in its operation against Iran.
Ahead of President Donald Trump's scheduled address to the nation on Iran, Rubio said the end of the US operation against Iran will come "not today and not tomorrow."
"We can see the finish line. It's not today, it's not tomorrow, but it is coming," Rubio noted.
On February 28, the United States and Israel launched strikes on targets in Iran, including in Tehran, causing damage and civilian casualties. Iran responded by striking Israeli territory and US military facilities in the Middle East.