"The essence of the problem in this matter is the North's nuclear and missile threats. If these threats are eliminated, the need to deploy the THAAD system would naturally disappear," Xinhua news agency quoted Park as saying.
It is the first time that South Korean leader mentioned the conditional THAAD deployment, showing signs of a slight change in her hard-line position ahead of her trips to Russia and China that have strongly opposed the US missile defence system in their neighbourhood.
Park is set to visit Vladivostok for two days to attend the second Eastern Economic Forum and hold a bilateral summit with Russian President Vladimir Putin. The forum was launched last year to speed up development of the Russian far east.
She will move to China to attend Group of 20 (G20) summit scheduled to be held in Hangzhou on September 4-5.
Park, however, reiterated that the THAAD deployment is a measure of self-defence to protect from North Korea's "ever-escalating" nuclear and missile threats.
Chinese and Russian objections to THAAD in South Korea came as the US missile shield's X-band radar can break strategic balance in the region and damage security interests of the two countries.
