President Biden said in an interview with CNN on Wednesday that if Israel invades the Gaza city of Rafah, the U.S. will stop supplying it with artillery shells, bombs for fighter jets and other offensive weapons.

Why is it matters: This is the first time that Biden or any other official in his administration has said publicly that an Israeli military ground operation in Rafah will result in a halt to the supply of offensive weapons to Israel.

Driving the news: More than a million Palestinians have taken refuge in Rafah in recent months.

• The Biden administration opposes a broad Israel Defense Forces ground operation in Rafah that would not include a credible plan to protect civilians.
• The administration has already put on hold a weapons shipment to Israel that included 1,800 2,000-pound bombs and 1,700 500-pound bombs, a senior U.S. official told Axios.

State of play: On Monday night, the IDF took control of the Rafah crossing in the eastern outskirts of the city of Rafah and began evacuating the population from several neighborhoods in the area. However, the IDF did not enter the city of Rafah itself.

• Biden said in the CNN interview that the IDF's action so far does not cross the red line he has set.
• "They haven't gotten into the population centers. What they did was right on the border, and it's causing problems with, right now, in terms of with Egypt," Biden told CNN's Erin Burnett.

Zoom in: Biden said in the interview that he told Israel's Prime Minister Benjamin Netanyahu and members of its war cabinet that they would not receive U.S. support if they entered the population centers in Rafah.

• He noted that civilians in Gaza were killed as a result of Israel's use of U.S.-made bombs in populated areas.
•  "I made it clear that if they go into Rafah — they haven't gone into Rafah yet — if they go into Rafah, I'm not supplying the weapons that have been used historically to deal with Rafah, to deal with the cities," Biden said.
• "We're not going to supply the weapons and artillery shells," Biden said.

Yes, but: The president emphasized that the U.S. will continue to provide Israel with defensive weapons such as funding for Iron Dome interceptors and other missile defense systems with which the Iranian attack on Israel was defeated.

• "We're not walking away from Israel security, we're walking away from Israel's ability to wage war in those areas," Biden said.

What's next: The full interview airs on CNN at 7pm ET.

Go deeper: Rafah assault threatens to be Israel breaking point for Democrats