Malaysia's Prime Minister Mahathir Mohamad, left, shakes hands with his Singaporean counterpart Lee Hsien Loong during a meeting at the Presidential Palace on the sidelines of the 33rd Association of Southeast Asian Nations (ASEAN) summit in Singapore on Nov. 12, 2018.

Singapore's foreign minister said on Monday ties with neighboring Malaysia have been in a "downward spiral" over a series of maritime and airspace disputes but hoped the issues could be resolved amicably.

Singapore's Vivian Balakrishnan and his Malaysian counterpart, Saifuddin Abdullah, met last week and agreed to take steps to de-escalate tensions over the air and maritime disputes.