NEW DELHI—India is willing to talk about the disputed territory of Kashmir with Pakistan as part of an effort to advance peace talks, India's top diplomat said, adding that Pakistan needs to take serious action against militants that use its soil to attack India.

The comments by Indian Foreign Secretary Ranjan Mathai, in an interview with The Wall Street Journal on Wednesday, suggest that a recent thaw in relations between the two countries could lead to discussions on the key territorial issue, which has been off the table since 2007.