Senators describe 'long and detailed' White House briefing on North Korea Trump invited the full Senate to the White House for a security briefing.

 -- Several Senate Republicans described the full Senate briefing on North Korea at the White House Wednesday as a thorough accounting of the administration's diplomatic and military options when it comes to dealing with Kim Jong Un.

Sen. Ted Cruz, R-Texas, called it "a long and detailed briefing."

"The military is obviously planning for a number of options, as they should -- minimal military action to more significant action," Cruz said. "It's of course the hope of the administration and Congress that military action isn't necessary. If there's a clear and imminent threat to the U.S., our military needs to be prepared to act and I believe they are prepared to act to keep our country safe."

The senators were invited at the personal invitation of President Donald Trump after Senate Majority Leader Mitch McConnell, R-Kentucky, requested a briefing. The president stopped by the briefing at the Eisenhower Executive Office Building on the White House grounds.

Sen. Cory Gardner, R-Colorado, said that one takeaway from the meeting was that "we are a long ways away from exercising all of our options on the diplomatic side."

"There were great questions within the briefing from both sides of the aisles," Gardner said. "It shows how important this issue is, to have that team assembled to talk about this and make sure North Korea knows they won't get away with this."

Separately, a senior administration official told ABC News that part of the current concern about North Korea comes from China's view of North Korea as a threat.

"I think what's different about how China is viewing the problem in North Korea today is that China is viewing that problem as the threat not only to U.S. interests and security or South Korean or Japanese interests and security, but also a threat to Chinese interests and security and so I think that is a big shift in and of itself," the senior administration official told ABC News.

White House officials say the South Auditorium would be turned into a Sensitive Compartmented Information Facility, or "SCIF," and the briefing will be led by Secretary of State Rex Tillerson, Secretary of Defense James Mattis, Chairman of the Joint Chiefs of Staff Joseph Dunford, and Director of National Intelligence Daniel Coats.

When asked about the bus ride to the White House ground for the meeting, Gardner said it was "a unique approach to a classified briefing."

Using the White House grounds for a full briefing with the Senate is a rare move, but administration officials told ABC News that too much shouldn't be read into the choice of location.

Officials said that after hearing of McConnell's request, the president suggested nonchalantly that the senators should come to the White House because he's a "gracious host." Trump has cultivated a reputation in his meetings at the White House for relishing the opportunity to show off his historic digs.

ABC News' Ali Rogin and Katherine Faulders contributed to this report.