(CNN) With its fourth missile test in four days, North Korea issued a stark reminder to the United States that its weapons program isn't going away.

Tokyo and Washington have requested an urgent meeting of the United Nations Security Council after Pyongyang launched a missile over the Japanese island of Hokkaido early Tuesday morning local time.

The meeting will take place Tuesday in New York, two UN diplomats told CNN.

In total, North Korea has fired 21 missiles during 14 tests since February , further perfecting its technology with each launch.

US President Donald Trump said Tuesday that "the world has received North Korea's latest message loud and clear," adding Pyongyang "has signaled its contempt for its neighbors, for all members of the United Nations, and for minimum standards of acceptable international behavior."

"Threatening and destabilizing actions only increase the North Korean regime's isolation in the region and among all nations of the world," he said in a statement. "All options are on the table."

North Korean state media has yet to acknowledge Tuesday's launch, but a recent commentary published by state news agency KCNA accused Trump of being a "source of headache(s) at home and abroad."

"Much upset by (North Korea's) successful ICBM test-launches, Trump ran riot, talking about 'fire and fury' unprecedented in the world," KCNA said, accusing Trump of adding "fuel to the aggravated situation."

More sanctions?

Though the meeting is on the agenda, it's not clear what the Security Council can do to stop North Korea firing off missiles.

Earlier this month , a new round of sanctions was levied against North Korea in an effort to stymie the country's ability to earn foreign money, some of which helps fund its weapons program.

However, rather than working to curb Pyongyang's missiles tests, the international pressure campaign seems to have hardened the regime's resolve.

"The bottom line is they flew a missile over a neighboring country without giving them a heads up," said John Delury, a professor at Yonsei University's Graduate School of International Studies.

"These North Korean missile tests are emblematic of the ongoing security dilemma where there are hostile parties taking steps to deter the other, and each improvement on one side's deterrent capability is a provocation to the other side."

Options

The Trump administration is pursuing a "peaceful pressure" campaign to push for the denuclearization of the Korean Peninsula.

The United States has said it doesn't seek regime change, but North Korea says it needs to develop its weapons program to prevent an imminent US invasion.

While the White House says diplomacy is preferred when it comes to dealing with Pyongyang, talks will not be unconditional and a military option remains "on the table."

US Secretary of State Rex Tillerson said that North Korea, which the United States has accused of reneging on previous agreements, must offer some sort of proof that it will negotiate in good faith.

He said last week at a State Department briefing that the recent lack of missile tests may have been "the signal we are looking for."

Why North Korea wants nukes and missiles North Korea has long maintained it wants nuclear weapons and long-range missiles in order to deter the United States from attempting to overthrow the regime of Kim Jong Un. Pyongyang looks at states like Iraq -- where former dictator Saddam Hussein was overthrown by the United States, and Libya -- the country's late leader, Moammar Gaddafi, gave up his nuclear ambitions for sanctions relief and aid, only to be toppled and killed after the US intervened in the country's civil unrest -- and believes that only being able to threaten the US homeland with a retaliatory nuclear strike can stop American military intervention. Many experts believe North Korea would not use the weapons first. Kim Jong Un values his regime's survival above all else and knows the use of a nuclear weapon would start a war he could not win, analysts say.

Tuesday's launch, however, has changed the game, argues Adam Mount of the Center for American Progress.

"If we had a window in August, that window is closed. That doesn't mean the talks are impossible, but it means it does require an even greater effort by the United States," he said.

Mount argues that the United States has not done a good enough job telegraphing what constitutes acceptable behavior from the North Koreans and what it should expect to receive.

Some of President Trump's comments — such as when he said North Korea would "be met with fire and fury " if the country continued to threaten the United States — may make for strong headlines, they are too broad to have any tangible deterrent effect, Mount said.

"The United States has not generated a coherent and forceful response to North Korea," Mount said. "If there's not a specific response that's tailored to this to deter this from happening in the future, it will continue to happen."

Bruce Bennett, a senior researcher at the RAND Corporation who specializes in North Korea, says the United States needs to reestablish its credibility with a targeted military response.

"That military action could include flying a Tomahawk cruise missile over North Korea and directly over Pyongyang to illustrate that two can play at this game," Bennett said.

"The United States needs to turn to a more incremental, multidimensional strategy that minimizes the likelihood of major North Korean escalation, but still hits back against North Korea, imposing significant costs," he said.

JUST WATCHED How much damage can North Korea's weapons do? Replay More Videos ... MUST WATCH How much damage can North Korea's weapons do? 01:04

Reality

After five nuclear tests and two successful launches of intercontinental ballistic missiles, most experts believe the opportunity to prevent North Korea from developing a nuclear weapon that could hit the United States has come and gone.

Attempts to take out weapons in North Korea -- where reliable intelligence is scarce -- could be incredibly risky.

"If you attack them after they have the nuclear weapons, it's not a preventive war. It's just a plain old nuclear war," Jeffrey Lewis, a nonproliferation expert at the Middlebury Institute of International Studies' James Martin Center for Nonproliferation Studies, said on a recent podcast.

Even if nuclear weapons aren't used, North Korea's huge artillery stocks could devastate the South Korean capital of Seoul and its surrounding areas. Japan's military likely does not have the capability to forcefully respond without US assistance, as it's a primarily defensive force.

Unconditional dialogue is one of the few remaining options that some North Korea watchers think should be tested.

The current process of clamping down on North Korea is what the country is used to, argues Delury of Yonsei University.

Punishing North Korea for its missile tests -- which the United Nations Security Council has barred it from conducting -- is "the logical counter-reaction but it doesn't change the outcome," Delury said. "You just continue along this trajectory."

"There's just really no good option," Robert Kelly, a professor of political sciences at South Korea's Pusan National University, told CNN.

"If there were, we wouldn't be talking about this every few months. No one knows what to do about North Korea."