The United States military says its controversial Thaad missile defence system is now operational in South Korea.

The system can intercept North Korean missiles although full operational capability is still some months away.

Tensions have been rising around the Korean peninsula, with repeated threats from North Korea and the presence of a group of US warships and a submarine.

North Korea reacted angrily to the latest military exercise, accusing the US of risking a nuclear war.

The rise in tension comes only a day after US President Donald Trump said he would be “honoured” to meet North Korean leader Kim Jong-un, in the right circumstances.

The system’s deployment to defend against a North Korean missile threat has become an issue in the South Korea’s upcoming presidential election and with China, which is concerned that the system’s long-range radar could track Chinese missile systems.

The Terminal High Altitude Area Defense (THAAD) is an advanced defensive anti-missile system that incorporates a long-range radar used to track incoming ballistic missiles in their terminal phase of flight.

The system consists of multiple missile batteries coordinated by a radar and tracking system. While now initially operationally capable it will not be fully operational for a few months.

The system’s deployment to South Korea was agreed to in July of last year, but the initial components of the THAAD system did not arrive in South Korea until the first week in March. The arrival coincided with a North Korea’s launch of multiple ballistic missiles.

The system’s deployment is receiving a mixed response in South Korea. Early last week protesters greeted the system’s components as they arrived at its operational location, a former golf course, located 130 miles southeast of Seoul.

On Wednesday Adm. Harry Harris, the commander of U.S. Pacific Command told Congress last week that the system would be operational “in coming days”.

The anti-missile system has also become an issue in South Korea’s presidential election being held on May 9.

Moon Jae-in, the leading presidential candidate, has criticized the THAAD deployment and believes that it should be up to a new administration to decide whether the system should be deployed.

The United States has maintained that the system is purely defensive, but China has criticized the system’s radar as a potential hedge to its ballistic missile development. China has placed sanctions on major South Korean businesses to show its disapproval of the system’s deployment.

“I find it preposterous that China would try to influence South Korea to not get a weapon’s system that’s completely defensive against the very country that’s allied with China,” Admiral Harris told a House panel last week. “If China wants to do something constructive then they ought to focus less, in my opinion, on South Korea’s defensive preparations focus instead more on North Korea’s offensive preparations.”

To that end, Harris told the same panel that he is encouraged by recent Chinese efforts to influence North Korea. Secretary of State Rex Tillerson said last week that China has warned North Korea it will impose sanctions if it conducts another underground nuclear test.

The THAAD missile system will add another layer of anti-missile defense for South Korea. The United States. military and South Korea both have Patriot anti-missile batteries that can defend against short range missiles.

Last week President Trump mentioned in an interview that it would be appropriate for South Korea to pay for the system’s deployment. “It’s a billion dollar system,” he told Reuters.

Lieutenant General H.R. McMaster, the national security adviser, told Fox News on Sunday that the United States would adhere to the agreed upon terms of the missile’s deployment.

“But what the president has asked us to do is to look across all of our alliances and to have appropriate burden-sharing, responsibility-sharing,” said McMaster. “We are looking at that with a great ally, South Korea. ”

“The question of what is the relationship on THAAD, on our defense relationship going forward, will be renegotiated as it’s going to be with all of our allies’ said McMaster.