MANILA - Foreign Affairs Secretary Alan Peter Cayetano on Sunday thanked United States President Donald Trump for his offer to mediate in sea disputes in the South China Sea, but said that Southeast Asian countries will need to arrive at a consensus before taking the deal.

"It is a very kind, generous offer because he is a good mediator. He is the master of the art of the deal. Claimant countries would have to answer as a group or individually and not one country can just give an instant reply," Cayetano told reporters on the sidelines of the Association of Southeast Asian Nations (ASEAN) Summit.

Before leaving Hanoi, Trump told Vietnamese President Tran Dai Quang that he was prepared to mediate between claimants to the South China Sea. Five ASEAN countries are contesting China's sweeping claims to the busy waterway where about $3 trillion in goods pass each year.

"If I can help mediate or arbitrate, please let me know," Trump said in comments at the start of a meeting with the Vietnamese leader.

• (READ: Trump offers to mediate in South China Sea dispute)

Cayetano did not directly answer if the Philippines and other Southeast Asian claimant countries need help from other global powers to deal with China, which has been reclaiming islands and positioning warships along disputed waters.

Cayetano also assured that relations between Manila and Beijing "are going well."

He said Chinese President Xi Jinping and Philippine President Rodrigo Duterte "spoke about the South China Sea issue and there were a lot of assurances from both sides" that we will "move forward on the code of conduct" to make the South China Aea a "sea of peace and stability."

Southeast Asian leaders and their counterparts are expected to announce the formal start of negotiations on the sea code that envisions to manage tensions in the disputed waters.

In August, ASEAN pushed for a legally binding code despite China's insistence for a document with lesser force.

Despite unresolved issues, discussions between ASEAN and China have improved, Cayetano said.

"We are making giant steps forward in talking about preserving marine life, having less navy and more coast guard and more cooperation," he said.

"I am not saying there are no problems; I am saying it is getting better," he added.