"As far as I know, the message was conveyed to North Korea yesterday in an appropriate manner," Chung told reporters at Incheon International Airport.

His remarks suggest that the two Koreas have operated a communication channel, probably at the DMZ village of Panmunjom or a North Korean diplomatic mission in New York.

Trump's birthday message also reflects his assertion of a good relationship with Kim despite a drawn-out stalemate in nuclear talks and Pyongyang's renewed saber-rattling.

Chung said he had carried Moon's message of respect and gratitude for Trump's leadership in connection with efforts to resolve the Korean Peninsula issue.

Trump gave Moon his regards as well.

Asked whether the sensitive issue of South Korea's possible role in the Strait of Hormuz was discussed in his meeting with Trump, Chung said there was "no direct mention" of it.

"There was a detailed briefing from the US side on the current Middle East situations," he said.

He reiterated the government's resolve to protect South Korean people and companies in the region and contribute to the international community's efforts for the freedom of navigation in the strait.

"(We) are still reviewing how to do so," he added.

Dispatching troops there is apparently among the options considered.

In the US capital, he also had talks with Deputy Secretary of State Stephen Biegun in the wake of a bilateral meeting with National Security Adviser Robert O'Brien and a trilateral session involving his Japanese counterpart, Shigeru Kitamura.

Chung described the discussions as "very useful," saying he had "very close consultations" on the establishment of permanent peace on the Korean Peninsula.

He was guarded about whether he had talked with US officials about Moon's overtures toward Pyongyang in his New Year's address earlier this week.

"I think there will be a chance later to explain" that to the media, he said. (Yonhap)