Japan's new prime minister, Yoshihide Suga, expressed hope for "forward-looking" relations with South Korea as "important neighbors" in his recent letter to President Moon Jae-in, Cheong Wa Dae said Monday.

Suga sent a reply to Moon on Saturday for his congratulatory message, as he was sworn in as the successor of Shinzo Abe, according to Cheong Wa Dae spokesman Kang Min-seok.

Suga said he hopes that the two sides will establish forward-looking ties by overcoming "difficult issues," Kang added without elaborating.

Suga was apparently referring to longstanding disputes over shared history, especially compensating victims of forced labor and sexual enslavement of women during Japan's colonial rule of Korea.

Moon earlier sent a letter to Suga, in which he proposed joint efforts to improve Seoul-Tokyo relations, shortly after his inauguration.

On Sunday, Suga reportedly had a phone conversation with US President Donald Trump.

Cheong Wa Dae officials have not announced when Moon will also talk with Suga on the phone. (Yonhap)