Reese Witherspoon And Sienna Miller Weigh In On Bradley Cooper's Plan to Address Gender Pay Gap

— -- Jennifer Lawrence started a conversation on Hollywood's gender pay gap that is drawing the attention of the industry's A-listers.

Reese Witherspoon is the latest star to contribute to the dialogue.

The Oscar winner applauded Bradley Cooper's recent decision to reveal his salary to his female costars to help them with their contract negotiations.

"That's great," Witherspoon told E! News at the L.A. County Walk to Defeat ALS. "I love to hear that."

"It's great that Hollywood is taking steps in the right direction," Witherspoon said, adding that every industry "should be talking about it."

Lawrence kicked off the discussion earlier this month, when she wrote in an essay on Lena Dunham's newsletter Lenny that she and "American Hustle" co-star Amy Adams got paid much less than their male co-stars Jeremy Renner, Christian Bale and Cooper.

The actors' pay was released publicly after Sony Pictures Entertainment was hacked in 2014.

"I didn’t get mad at Sony," wrote Lawrence. "I got mad at myself. I failed as a negotiator because I gave up early. I didn’t want to keep fighting over millions of dollars that, frankly, due to two franchises, I don’t need."

Cooper was quick to support his co-star.

"There's a double standard in the whole world, yeah, for sure. This is just one aspect," Cooper told E! News. "Anytime there's a place where a voice can come out and be outspoken -- something Sienna (Miller) did, or Jennifer -- that's great. ... I think it is making a difference."

A day later, Cooper went one step further, telling Reuters he would team up with his female co-stars in future productions to negotiate salaries.

"That's something that I could do," he said.

Meanwhile, Sienna Miller, who stars with Cooper in "Burnt," opened up about her experience with being offered less than her male co-star in a Broadway play.

"It was a situation where there were two people in a play and I was offered less than half what the male was offered," Miller told "Good Morning America" today. "It would felt undignified for me."

So Miller walked away.

"I think everybody has to come together to do something," Miller said when asked about Cooper's idea. "I think it's outrageous in this day and age, when women are doing the same jobs as men that we are undervalued to that degree. But I also think that it comes from within women. And I think there is a global conversation happening that is really inspiring. But it's going to take sacrifice."

She added, "I really wanted to do that play. I'm really sad I can't do it. But ultimately, we have to make -- we have to make changes."