WASHINGTON (Reuters) - U.S. lawmakers said high-profile briefings by the Trump administration on North Korea on Wednesday failed to provide the firm strategy they had hoped for dealing with what they described as a major national security threat.

Slideshow ( 10 images )

As a standoff escalated over the reclusive Asian nation’s development of nuclear weapons and long-range ballistic missiles, President Donald Trump welcomed all 100 members of the Senate to a highly unusual meeting at the White House complex, with Secretary of State Rex Tillerson, Secretary of Defense Jim Mattis, Director of National Intelligence Dan Coats and Marine General Joseph Dunford, chairman of the Joint Chiefs of Staff.

While administration officials often travel to the Capitol to brief lawmakers on national security issues, this time the entire Senate hopped on buses to the White House.

Vice President Mike Pence and the four officials later briefed the House of Representatives. That classified meeting took place in a secure auditorium at the Capitol complex.

The briefings came as Trump tries to put the best face on his first 100 days in office. He has signed executive orders to roll back Democratic policies but the period has been defined by an absence of any major legislative achievements.

A few Democrats dismissed the Senate White House “field trip” as little more than a photo opportunity.

Some Republicans were a little more enthusiastic.

“It was an OK briefing,” Senator Bob Corker, the Republican chairman of the Senate Foreign Relations Committee, told reporters as he arrived back at the Senate. “I’m not certain I would have had the briefing today,” he said.

Asked if the administration had a firm strategy, Senator John McCain, who chairs the Armed Services Committee, said, “They’re developing one.”

This week, Trump has discussed North Korea with U.N. ambassadors, increased the U.S. military presence in the region, and leaned on China to pressure Pyongyang. Tillerson will chair a U.N. Security Council meeting on Friday to discuss tougher sanctions.

After their briefing, members of the House expressed confidence in the administration officials who spoke, but some said they had real concerns.

Representative Brad Sherman, a senior member of the House Foreign Affairs Committee, said he was not convinced that the administration would do enough to control Pyongyang.

“I regard that level of resolve as very modest, weak and maybe even phony. The only way to put enough pressure on North Korea is to get China to do it,” Sherman told reporters.

Mac Thornberry, chairman of the House Armed Services Committee, said the administration wants to use “a variety” of tactics to push North Korea to give up its nuclear ambitions and said he agreed that all options must be on the table.

“We have to have incredible military presence in the region, including missile defense, especially for this regime,” he said.