"It's so terrible," Trump said at the White House. "I get along with both, I know both very well, and I want to see them work it out. I want to see them stop.

"They've gone tit-for-tat, so hopefully they can stop now."

Trump's comments came as India and Pakistan exchanged heavy artillery fire along their contested frontier, after New Delhi launched deadly missile strikes on its arch-rival.

At least 43 deaths were reported in the fighting, which came two weeks after New Delhi blamed Islamabad for backing an attack on the Indian-run side of disputed Kashmir, which Pakistan denied.

Pakistan has long been a key US military ally but Trump has been keen to build up relations with Indian Prime Minister Narendra Modi, whom he hosted at the White House in February.

"We get along with both countries very well, good relationships with both, and I want to see it stop," Trump said in the Oval Office.

"And if I can do anything to help, I will be there."

Trump initially played down the crisis as part of old tensions between India and Pakistan -- even saying they had been at odds for 1,500 years, despite the two countries only forming after independence from Britain in 1947.

But his administration has scrambled into action in the last 24 hours since the Indian strikes.

US Secretary of State Marco Rubio spoke to his counterparts from India and Pakistan on Friday, encouraging them to reopen dialogue to "defuse" the situation, the White House said.