WASHINGTON -- Scientists and security experts studying North Korea’s nuclear test on Tuesday believe the rogue nation is closing in on being able to place a nuclear weapon atop a missile and loft it at another country.

That, all believe, immediately raised the stakes of the dangerous game the North Koreans have been playing for the past decade. The problem for the United States is that with each North Korean advance, the possible U.S. responses decrease and get more aggressive. In fact, some experts believe the options now are just two: a pre-emptive strike on North Korea’s nuclear facilities or targeting any rocket or missile not long after it leaves the launch pad.

“What matters in these tests aren’t the missiles or even the devices, it’s the North Korean intent,” said Stephen Long, an international security expert at the University of Richmond in Virginia. “These are just the latest moves in a long game North Korea is playing. It’s an attempt to gain leverage.”

Experts agree the most recent moves have been impressive.

It was only 2002 when North Korea acknowledged a secret nuclear program, and only 2006 when it had its first underground test.

As recently as April 2012, the North Koreans appeared to be continuing a pattern of failure in their rocket technology, as a barely disguised attempt at a long-range missile launch broke apart early. But if that test failed almost completely, their December test of the same style of missile, the Unha-3, was a shocking success, a strong step toward developing something that someday could threaten American shores.

And then came Tuesday’s nuclear test, in which the North Koreans claimed to have miniaturized their device – a key step toward being able to place a nuclear payload atop a rocket.

Philip Coyle III, a former associate director for national security in the White House Office of Science and Technology, said that while concerns have ebbed and flowed about the nuclear ambitions of North Korea, “It’s not too early now to worry about it.”

Unlike Iran, which the U.S. accuses of working to develop a nuclear weapons capability, North Korea “already has it.” The thinking in defense circles, he said, is clearly becoming “you wouldn’t want to wait until they launched to deal with this problem.”

Frank von Hippel, a Princeton University professor and a former White House science adviser, guessed a warhead that could fit aboard a North Korean rocket would weigh about a ton.

“We may have to learn to live with them” as a nuclear weapons power, he said.

David Albright, a former U.N. nuclear weapons inspector who heads the Institute for Science and International Security, a Washington policy institute, said that even before the test, he’d assessed that North Korea could develop a warhead for its No-Dong rocket, a ballistic missile with a range of 800 miles, which puts Japan within its range. “They could just use it to create some real heartburn,” he said.

Albright said it’s still possible to pressure the North Koreans to resume meaningful disarmament talks, which were broken off in 2009, but that President Barack Obama would have to end the “strategic patience” policy of refusing negotiations until Pyongyang suspends its nuclear weapons program. Any successful negotiations would take a united international front and would need Chinese backing.