The Senate took part in a rare White House briefing on Wednesday to hear what senior leaders described as "an urgent national security threat" posed by North Korea's nuclear and missile programs.

The hour-long secret session for all senators was held at the Eisenhower Executive Office Building, next to the White House, and included a brief appearance from President Trump who made short, introductory remarks.

Marine Corps Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, also took part in the session. His presence is an indication that military options for dealing with North Korea likely were discussed.

New steps by the administration will include the imposition of additional economic sanctions.

"The United States seeks stability and the peaceful denuclearization of the Korean peninsula. We remain open to negotiations towards that goal. However, we remain prepared to defend ourselves and our allies," Defense Secretary Jim Mattis, Secretary of State Rex Tillerson, and Director of Intelligence Dan Coats said in a joint statement after the briefing.

Trump's approach seeks to pressure North Korea into dismantling nuclear, ballistic missile, and proliferation programs through imposing tighter economic sanctions and diplomatic measures, the three leaders said.

The senior officials noted that past efforts to halt the North Korean illicit arms programs had failed.

"With each provocation, North Korea jeopardizes stability in Northeast Asia and poses a growing threat to our allies and the U.S. homeland," they stated.

Sen. John Barrasso (R., Wyo.) told MSNBC the meeting was "very consequential" and included discussion of North Korea's shift from liquid to solid fuel missiles, and improving nuclear weapons and missile capabilities.

Barrasso said he favors increasing sanctions, including sanctions on China.

Sen. Chris Coons (D., Del.) called the session "very clear-eyed, sober and serious."

Coons told MSNBC the administration is working to avoid a conflict and "making it clear to China how serious we are about preventing North Korea from developing the capability to deliver a nuclear warhead by ICBM against the United States or one of our key allies, and that there are real efforts being made to avoid a misunderstanding or miscalculation because I do think this is a very dangerous circumstance and situation."

The administration recently completed a review of North Korea policy. New policies under consideration are imposing so-called secondary sanctions on North Korea that would be designed to cut off supplies of missile and nuclear goods from places such as China and Russia.

A U.N. panel of experts revealed in a report in February that debris obtained from a North Korean missile flight test last year included Chinese and Russian components.

President Trump pressed Chinese leader Xi Jinping during the recent summit meeting in Florida to pressure North Korea into giving up its nuclear arms and long-range missiles.

During the meeting, Xi told the president that China does not have the leverage over the Kim Jong Un regime in Pyongyang that the U.S. government believes it has, according to a White House official.

China has limited purchases of coal from North Korea but so far has not used its ability to restrict fuel oil exports to North Korea to pressure the regime.

North Korea relies on China for as much as 90 percent of its foreign trade.

White House officials and congressional aides sought to play down the significance of the briefing that comes amid heightened tensions. But all the officials said the threat from North Korea remains serious.

"I think it's really an expression of how seriously the president is taking this, and that he wants to engage with Congress on it," a senior administration official said of the session that has been scheduled for some time and is not a response to any particular event.

The aircraft carrier strike group led by the USS Carl Vinson is expected to arrive near the Korean peninsula in the next day, and a U.S. missile submarine also has been deployed.

The Air Force Strike Command also announced that a U.S. long-range nuclear missile was test fired from Vandenberg Air Force Base, California, on Wednesday. The command called the test of a Minuteman III intercontinental ballistic missile "an important demonstration of our nation's nuclear deterrent capability."

The deployment comes as U.S. intelligence agencies are closely watching North Korea for signs of another underground nuclear test, or a long-range missile test.

North Korea earlier this week carried out a large-scale live-fire artillery drill with some 300 to 400 artillery pieces firing into the sea.

North Korea has amassed a large percentage of its forces, including hundreds of artillery pieces along the demilitarized zone separating North and South Korea. The artillery is within range of the South Korean capital of Seoul.

"We are engaging responsible members of the international community to increase pressure on the DPRK in order to convince the regime to de-escalate and return to the path of dialogue," Mattis, Tillerson and Coats said, using the acronym for North Korea.

"We will maintain our close coordination and cooperation with our allies, especially the Republic of Korea and Japan, as we work together to preserve stability and prosperity in the region."