U.S. President Donald Trump vowed Sunday to resolve the Afghanistan-Pakistan crisis “very quickly” as peace talks between the two rivals entered their second day.

The two countries are embroiled in a bitter security row, with each side saying they were responding to aggression from the other during clashes earlier this month.

It was the deadliest fighting between them in several years, marking a low point in relations while also causing alarm in a region where armed groups like al-Qaida are trying to resurface.

Pakistan accuses Afghanistan of turning a blind eye to terrorists who cross the border for attacks, a charge the country’s Taliban rulers reject.

The second round of talks between them began in Istanbul on Saturday, focusing on transforming a fragile cease-fire, achieved earlier this month in Doha, into a durable framework for peace and border security.