President Obama shakes hands with President-elect Donald Trump in the Oval Office of the White House in November. (AP Photo/Pablo Martinez Monsivais)

Amid increasing tensions with North Korea, President Trump has taken to Twitter to highlight comparisons between his leadership and that of former president Barack Obama, including an unscientific, nearly week-old poll asserting he is the better president.

Starting on Wednesday night, the Republican president retweeted a series of Twitter posts related to his Democratic predecessor, starting with one by John Bolton, a former U.S. ambassador to the United Nations and Fox News contributor, who said the United States is at risk because of Obama.

“Our country & civilians are vulnerable today because Barack Obama did not believe in national missile defense. Let’s never forget that,” Bolton said in the tweet that Trump retweeted.

The president also retweeted “The Five,” a Fox News program, which quoted host Jesse Watters as saying that Trump “being unpredictable is a big asset.”

“North Korea knew exactly what President Obama was going to do,” Watters added.

The Fix's Aaron Blake looks at how President Trump's threats to North Korea contrast with the milder tone of his Cabinet secretaries. (Jenny Starrs,Bastien Inzaurralde/The Washington Post)

Trump, who has threatened “fire and fury” if North Korea continues its provocations, returned to the subject of Obama on Thursday morning, retweeting a survey by ProgressPolls, which asked: “Who is a better President of the United States?”

The organization asks its 123,000 Twitter followers for thoughts of a variety of “tough questions,” a method that does not produce scientific polling results.

It tweeted on Aug. 4 that 61 percent thought Trump was better, compared to 39 percent who thought Obama was better.

Trump, who is in the middle of a 17-day working vacation at his private golf club in Bedminster, N.J., has not commented on any of the tweets himself.