Sen. Dianne Feinstein said Tuesday that President Trump's "bombastic" threats to North Korea over its nuclear weapons program are not "helping" to defuse the situation.

Feinstein, D-Calif., in a statement, said the U.S. should engage in diplomatic negotiations with North Korea without any preconditions over its nuclear weapons program. Earlier Tuesday, Trump threatened to unleash "fire and fury" against North Korea if it continues to threaten the U.S. with its weapons program.

"Isolating the North Koreans has not halted their pursuit of nuclear weapons. And President Trump is not helping the situation with his bombastic comments," Feinstein said. "The United States must quickly engage North Korea in a high-level dialogue without any preconditions. In my view, diplomacy is the only sound path forward."

Feinstein, the former chairwoman of the Senate Intelligence Committee, issued her statement in reaction to Trump's comments, and news reports Tuesday that North Korea has successfully produced a miniaturized nuclear warhead that can fit inside its intercontinental ballistic missiles.

Rep. Eliot Engel, D-N.Y., also criticized Trump's threat, charging that the president has drawn an "absurd red line."

"Make no mistake: North Korea is a real threat, but the president's unhinged reaction suggests he might considering using American nuclear weapons in response to a nasty comment from a North Korean despot," said Engel, the ranking member of the House Foreign Affairs Committee, in a statement. "America's security is based not just on the strength of our armed forces but on the credibility of our commander-in-chief. Today, President Trump's reckless behavior and impulsive outburst undermined the security of the American people, and that of our friends and allies. Kim Jung Un will call his bluff as America's adversaries watch."

Trump's threat to North Korea came hours after Pyongyang escalated its criticism of the U.S. and threatened to conduct another missile test in response to sanctions the United Nations Security Council unanimously approved on Saturday.

Pyongyang test-fired its second intercontinental ballistic missile late last month, which some experts said was capable of reaching parts of the U.S.

Secretary of State Rex Tillerson has said the Trump administration wants to use sanctions to force North Korea to negotiate an elimination of their nuclear program.