North Korea's launch of an intercontinental ballistic missile does not bring the United States closer to war with the rogue regime, Defense Secretary Jim Mattis said Thursday.

Trump administration efforts to hold the North accountable and halt its efforts to develop a nuclear-tipped ICBM capable of hitting the U.S. mainland, he added, are "purely diplomatically led."

Earlier in the day in Poland, President Trump said he was considering "pretty severe" responses to the ICBM launch. A day earlier, Ambassador to the U.N. Nikki Haley called the long-range missile test a "clear and sharp military escalation" during an emergency Security Council meeting, and warned that the window for diplomatic action against North Korea was closing.

Mattis appeared to soften the rhetoric in an impromptu visit with reporters at the Pentagon on Thursday.

"I do not believe this capability in itself brings us closer to war because the president's been very clear, and the secretary of state's been very clear, that we are leading with diplomatic and economic efforts," Mattis said.

The secretary said the military is ready to respond and to uphold security alliances with Japan and South Korea.

"We stand ready to provide options if they are necessary," Mattis said. "The military maintains military options for the commander in chief."

In response to questions about Trump's statement, the secretary said, "Any effort by North Korea to start a war would lead to severe consequences."

North Korea made a leap forward in its burgeoning missile program Monday with the successful test of the ICBM, something Trump said would not happen. The missile was a new type the Pentagon had not seen before and may have been capable of reaching Alaska.

The regime hopes to create a nuclear warhead that can be carried by its missiles, potentially endangering the U.S. mainland.

The Trump administration is pressing for China, which maintains economic ties with North Korea, and other countries to support stronger sanctions on the regime that could force it to give up its missile ambitions, but Haley said a military response remains an option.

The U.S. military responded to the launch on Tuesday with a joint South Korea missile exercise, shooting a barrage into the sea off the Korean peninsula.