Japan and South Korea agreed to resume regular visits between their leaders and take steps to resolve a trade dispute during a highly anticipated summit Thursday, in what Japan’s prime minister called a “big step” to rebuilding the two nations’ security and economic ties as they try to overcome a century of difficult history.

The summit could revise the strategic map of northeast Asia. The two U.S. allies, who have long often been at odds over their history, are seeking to form a united front, driven by shared concerns about a restive North Korea and a more powerful China.