The United States pledged Tuesday to put unrelenting pressure on the "leadership of North Korea" after the communist nation carried out banned ballistic missile launches in defiance of international pressure.

 The North fired the three missiles -- two of them short-range Scud and the third an intermediate-range Rodong -- earlier Tuesday in what was seen as a show of force against the planned deployment in South Korea of the U.S. THAAD missile defense system.

"This is just another in a series of provocations that raises the concerns of the international community and frankly only strengthens our resolve to continue to put pressure on the leadership of North Korea to suspend all activities related to its ballistic missile program," State Department spokesman Mark Toner said at a regular briefing.

"We're going to keep the pressure on. We've got a strong sanctions regime that we strengthened even further recently after missile tests and nuclear tests. And we're going to continue to apply pressure and we're going to continue to call on North Korea to stop its provocative actions and respond to the international community's concerns," he said.

Toner also stressed the importance of fully carrying out existing sanctions.

"We're always looking at ways we can continue to apply pressure and what we talked about frankly is the sanctions are pretty severe right now. What matters is how we enforce those sanctions and that actually involves better coordination among all the countries in the region and that includes China," he said.

The U.S. has sought to increase pressure on the North, leading the U.N. Security Council to adopt the toughest sanctions ever on Pyongyang and enacting its own unilateral sanctions on the communist nation in the wake of the North's fourth nuclear test in January and a long-range rocket launch the following month.

Last month, the U.S. Treasury Department also designated the North as a "primary money laundering concern," a powerful sanction designed to cut off the provocative regime from the international banking system for defiantly pursuing nuclear and missile development.

And earlier this month, the U.S. also imposed first-ever sanctions on North Korean leader Kim Jong-un for his roles in the country's human rights abuses. Pyongyang has protested the blacklisting, denouncing it as a declaration of war and vowing to cut off the only diplomatic channel via its mission to the United Nations.

The North has also protested a joint decision by Seoul and Washington to deploy a Terminal High Altitude Area Defense (THAAD) battery in the South, claiming it's part of a plot to invade the country and threatening to take "physical" counteractions against it.

White House press secretary Josh Earnest said the U.S. has been working effectively with its partners in the region to apply significant pressure to the North. Though the pressure has not led to the North making a strategic decision, it has deepened Pyongyang's isolation, he said.

"What is clear is that North Korea is isolated like never before. The international community is united like never before.

Hopefully, that will lead to a situation where North Korea makes a strategic decision to come out of the shadows of the international community and try to rejoin international community," Earnest said.

"But before we can do that, they're going to have to make a clear commitment to ending these kinds of provocations and abiding by the U.N. Security Council Resolutions that govern both their nuclear weapons program and their ballistic missile program," he said. (Yonhap)