Washington (CNN) The US anti-missile system designed to mitigate the threat of North Korea's missiles will soon be operational, US and South Korean defense officials said.

US Pacific Command chief Adm. Harry Harris told the House Armed Services Committee on Wednesday that the Terminal High Altitude Area Defense (THAAD) missile defense system would be "operational in the coming days to be able to better defend South Korea against the growing North Korea threat."

Parts of the system have already been moved to the planned deployment site, the South Korean Defense Ministry said

THAAD was deployed to South Korea by the US in response to North Korea's increased missile and nuclear tests, but the defense system drawn sharp opposition from China and Russia, who see it as also potentially neutralizing their nuclear deterrents.

The original goal was to have the complete system fully operational by the end of this year, but the US and South Korea have publicly stressed the need to speed up the deployment of the technology as tensions have mounted with Pyongyang.

"Currently, the basic goal is to promote the full operational capability of one turret by the end of this year," South Korean Defense Ministry spokesman Moon Sang-kyun said at a briefing.

He said that equipment, including launchers, combat control stations and radar, had been deployed to the site in North Gyeongsang province and would be imminently operational.

"These things are now in place, so you can connect them to get the operational capability from early on -- that's what 'within days' means."

He added that the current deployment was not a "pilot operation" for the full rollout of the missile system, but is "capable of actual reaction to North Korea's provocation."

South Korean presidential candidate Moon Jae-in, who is expected to win the country's election on May 9, has called for deployment to be discontinued until the election is over

US admiral: Chinese opposition 'preposterous'

Harris said it was "preposterous" that China would take economic steps to try to stop South Korea from receiving a defensive system , which the US insists does not pose a threat to Beijing.

He added that China appears to be working to deter North Korea, as President Donald Trump has pushed his Chinese counterpart to do.

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"I'm reasonably optimistic now that China is having an influence, and they are working in the right direction with regards to North Korea thanks to the efforts of our president and theirs," Harris said.

The Pacific commander said that he was taking Kim Jong Un at his word that the North Korean leader is determined to develop a long-range nuclear missile that could strike the US and that should "provide us all a sense of urgency" to ensure US forces in the Pacific are prepared.

He said providing "credible combat power" was the best way to ease tensions on the Korean Peninsula.

"We want to bring Kim Jong Un to his senses, not to his knees," Harris said.

Harris says USS Vinson slip-up 'his fault'

The Pacific commander cited the USS Carl Vinson carrier strike group deployment to northeast Asia as such a deterrent against North Korea's rising threats, saying it was now in the Philippine Sea and "in strike range and power projection range of North Korea if called upon to do that."

The Vinson is headed north after initial confusion earlier this month about the location of the carrier, a miscommunication Harris accepted responsibility for.

"That's my fault on the confusion, and I'll take the hit for it," Harris told the panel.

He said it was his decision "to pull the Carl Vinson out of Singapore, truncate the exercise it was going to do south of Singapore, cancel its port visit to Australia and then proceed north."

He added, "Where I failed was to communicate that adequately to the press and the media. So that is all on me." Harris did not address what, if any, communications took place with the White House.

As another deterrent, Harris pointed to the USS Michigan -- a guided-missile submarine -- that arrived in South Korea Tuesday, saying it was an important show of force.

"We have a lot of preemptive options," Harris said.

Harris: We need more submarines

At the same time, Harris talked up his command's unfulfilled needs. He said he only had 50% of the submarines he sought for the region -- "We need more submarines," he said bluntly -- and that he saw a need for more interceptors deployed in California and Alaska to defend against potential North Korean missiles.

He also said he'd be interested in deploying missile-defense radars to Hawaii -- and possibly missile interceptors -- to help better defend the islands from North Korea's missiles.

Harris' testimony comes ahead of two congressional briefings on North Korea Wednesday afternoon, where Defense Secretary James Mattis, Joint Chiefs Chairman Gen. Joe Dunford, Secretary of State Rex Tillerson and Director of National Intelligence Dan Coats will brief the full House and Senate.

Senators are headed to the White House for the briefing, where President Donald Trump may drop in.

While the briefings are being held in a classified setting, House Armed Services Chairman Mac Thornberry of Texas said Harris' testimony was important for reassuring the public.

"I think the public is nervous, and they need to know that we have the military capability to prevail should a conflict come," Thornberry said ahead of the hearing.

Harris is testifying in three congressional hearings this week, but he's doing so without Gen. Vincent Brooks, the head of US Forces Korea, who was supposed to testify but remained in the Pacific due to the increased tensions.