Trump, in Hanoi as part of a 13-day Asia trip, at a later news conference on November 12 brought up sanctions against Russia, saying Moscow had been "very heavily sanctioned" and that "it's now time to get back to healing a world that is shattered and broken," RFE/RL reported.

The United States has placed sanctions on Russia for its alleged interference in the 2016 U.S. presidential election and has joined with other Western countries in imposing them against Moscow for its aggression in Ukraine.

Read alsoMajor Russian defense, intelligence companies targeted by new U.S. sanctions listHe did not explain his sanctions comments further or specifically suggest any easing of them.

He also attempted to clarify earlier statements he made about Russian tampering in the U.S. election, saying he believed U.S. intelligence agencies’ assessment but that he also believed Russian President Vladimir Putin was sincere in his denials about the meddling.

In his Twitter comments, Trump attacked "all the haters and fools" who have criticized his attempt to improve relations with Russia and Putin in particular.

"When will all the haters and fools out there realize that having a good relationship with Russia is a good thing, not a bad thing," he wrote.

"There [sic] always playing politics – bad for our country. I want to solve North Korea, Syria, Ukraine, terrorism, and Russia can greatly help!"

In another tweet, Trump asserted that his 2016 presidential election rival, Hillary Clinton "was begging Russia to be our friend" when she was secretary of state, and that President Barack Obama also tried to improve ties with Moscow but "had zero chemistry with Putin."

Trump also wrote that China had agreed to help pressure North Korea over its nuclear-weapons program.

Trump tweeted that Chinese President Xi Jinping "has stated that he is upping the sanctions against [North Korea]. Said he wants them to denuclearize. Progress is being made."

Trump also responded to comments made by North Korean leader Kim Jong Un, who had called him a "lunatic old man."

"Why would Kim Jong-un insult me by calling me 'old,' when I would NEVER call him 'short and fat?' Oh well, I try so hard to be his friend – and maybe someday that will happen!" he wrote.

Trump a day earlier said an agreement with Putin on Syria would save many lives after the two met at a summit of Asia-Pacific leaders in Danang, Vietnam.

"We agreed very quickly," Trump told reporters aboard Air Force One as he flew from Danang to Vietnam's capital, Hanoi.

"It's going to save tremendous numbers of lives," he said of the agreement announced by the Kremlin in a joint statement on its website.

Separately, Putin told journalists at the end of the summit that the joint statement "is extraordinarily important" and confirmed the principles of the antiterrorism fight.

The statement said Trump and Putin had agreed on the sidelines of the APEC summit that a political solution was needed on Syria and that they would continue efforts to fight the Islamic State (IS) militant group.

Russia and the United States agree there is no military solution to the Syrian conflict, the joint statement said.