WASHINGTON – Lashing out at probes into his 2016 campaign and Russian election interference, President Donald Trump said Friday that investigators ought to look into a book deal signed by former President Barack Obama and Michelle Obama.

"Let's look into Obama the way they've looked at me," Trump told reporters in the Oval Office. "Let's subpoena all of his records."

Though Trump didn't elaborate, he appeared to be referencing reports that the Obamas secured a $60 million advance for one book written each by Michelle and Barack Obama. The former first lady's book, "Becoming," was published last year and quickly became a best seller.

After summoning reporters to the Oval Office unexpectedly, the president sounded off on several issues:

Trump said his administration reached a "safe third country" agreement with Guatemala designed to reduce the number of migrants claiming asylum in the United States. If the agreement is finalized, migrants who cross into Guatemala en route to the United States would have to apply for asylum there instead of the U.S.

The president said he was not "spun up" on a recent missile launch by North Korea. Critics have questioned whether the missile launches undercut the president's approach with Kim Jong Un. Trump has said the recent missile launches have tested smaller weaponry than before. "My relationship is very good with Chairman Kim and we'll see what happens but they are short-range missiles," Trump said.

Trump said he had spoken by phone with the new British Prime Minister Boris Johnson. Trump described Johnson, a key figure in the U.K'.'s expected break with the European Union, as a friend. "I predict he will be a great prime minister," Trump said.

The president's reaction followed a high-profile hearing on Capitol Hill this week featuring former special counsel Robert Mueller. Trump, who acknowledged watching much of that hearing, has repeatedly criticized Democrats for holding it.

"All they want to do is impede, they want to investigate, they want to go fishing," Trump said. "There is no collusion, there is no obstruction, they have nothing. It's a disgrace."

During the hearing, Mueller largely summarized the report of his findings released in April. While he said investigators did not gather sufficient evidence to prove a conspiracy, he said that "problematic is an understatement" to describe some of Trump's conduct. Specifically, Mueller reinforced his conclusion that his investigation had "not exculpated" Trump on the question of whether he sought to obstruct justice by trying to impede the investigation.

Trump didn't limit his criticism of former President Obama to the book deal. He also took issue with a heating and cooling system installed by his predecessor.

"Now that they did the system," Trump said. "It's freezing or hot in here."