Former President George W. Bush said Thursday that "there's pretty clear evidence that the Russians meddled" in the 2016 American presidential election.

While never mentioning President Donald Trump by name, Bush appeared to be pushing back on Trump's decisions on immigration, as well as trying to have warmed relations with Russia.

"There's pretty clear evidence that the Russians meddled," Bush said at a talk in Abu Dhabi, the capital of the United Arab Emirates. "Whether they affected the outcome is another question."

Bush also said that "it's problematic that a foreign nation is involved in our election system. Our democracy is only as good as people trust the results."

U.S. intelligence agencies have concluded Russia meddled in the 2016 election to help Trump win. Numerous investigations are under way to determine whether Trump's campaign aided the Kremlin in its efforts.

Trump has repeatedly denied any "collusion" with Russia.

Speaking of Russian President Vladimir Putin, Bush called him "zero-sum."

"He's got a chip on his shoulder," Bush said of Putin. "The reason he does is because of the demise of the Soviet Union troubles him. Therefore, much of his moves (are) to regain Soviet hegemony."

Bush also stressed the need to back NATO and other alliances the U.S. has with the world.

Putin "is pushing, constantly pushing, probing weaknesses," the former president said. "That's why NATO is very important."

Bush also said that the United States needs to reform its immigration law.

Bush in 2008 became the first sitting U.S. president to visit the UAE. He spoke Thursday at a summit in Abu Dhabi put on by the Milken Institute, an economic think tank based in California.

He made his comments while in a conversation with Michael Milken, known as the king of high-risk "junk" bonds in the 1980s, pleaded guilty to securities-law violations in 1990 and served 22 months in prison. He agreed in a settlement with the SEC to a lifetime ban from the securities industry and paid a $200 million fine.

Milken, who is a prostate cancer survivor, and his family have given hundreds of millions of dollars away in recent decades. Forbes magazine estimates Milken, 71, is now worth some $3.6 billion.