Trump agreed on Friday to meet with Kim Jong-un by the end of May and the two Koreas are due to hold their own summit by the end of April.
North Korea has yet to respond to South Korean business people's wish to visit their factories in the Gaeseong Industrial Complex in the North's border city.
"I feel they're approaching this matter with caution and they need time to organize their stance".
Xi did not say more about the North Korean nuclear crisis, but he said China's relations with South Korea have "maintained a good momentum of improvement".
South Korea's National Security Office chief Chung Eui-yong and National Intelligence Service head Suh Hoon returned to Seoul on Sunday after meeting with Trump in Washington.
Xi said Chung had achieved "positive results" in his visits to North Korea and the United States last week, which led to the diplomatic breakthrough.
The two top diplomats "plan to share their assessment of the recent rapid progress on the Korean Peninsula and to have in-depth consultations on how to closely cooperate on denuclearizing the peninsula as well as on (envisioned) inter-Korean and US-North Korea talks", the Ministry of Foreign Affairs said.
South Korean envoys are visiting Japan, China and Russian Federation to brief the countries on planned inter-Korean talks and a meeting between North Korea's leader Kim Jong Un and US President Donald Trump.
"My main message today is that any advancement on the security dialogue should be accompanied by a parallel expansion on the human rights dialogue", he told the world body's Human Rights Council.
The North's official news agency has been lauding efforts between the North and South to thaw relations, but state media has continued to warn the United States and Japan against war-mongering.
Rhetoric in the North's state media has been tame, however, compared to threats past year that went as far as saying Pyongyang would fire missiles into the vicinity of the USA territory of Guam if provoked.