U.S. President-elect Donald Trump on Thursday reaffirmed Washington's security commitment to South Korea during his telephone conversation with South Korean President Park Geun-hye, an official source said.

During the talks that lasted some 10 minutes, Trump was quoted as saying that the United States will maintain a "firm, strong" defense posture to defend its Asian ally South Korea. The talks took place at around 10:00 a.m.

Trump added that Washington will work together with Seoul "until the end" for the security of the United States and South Korea, according to the official.

In response, Park congratulated him on his electoral win, stressing that South Korea and the U.S. have built trust based on the alliance while weathering a series of challenges together over the past six decades. She also pointed out that the alliance has served as a "cornerstone" of peace and prosperity in the Asia-Pacific.

"I expect that (we) can strengthen and develop the alliance down the road for the shared interests in various areas," she was quoted as saying during the phone talks.

Trump, in turn, said that he agreed with Park's remarks "100 percent."

The South Korean leader, then, pointed to North Korea's nuclear issue as the "greatest threat" facing the two nations.

"Given that in the past, North Korea staged provocations during the period of the government transition in the U.S., we need to closely cooperate in advance to thoroughly deter possible North Korean provocations and respond sternly if provoked," she said.

The source said that Park the stressed the need to employ strong sanctions against the communist state to pressure it into renouncing its nuclear ambitions.

The phone talks between Park and Trump came amid concerns about a potential shift in bilateral security and economic relations.

The phone conversation came less than a day after Trump was declared with winner of the hotly contested race for the White House. The talks came earlier than expected and reflects the importance placed by the two sides on the decades-old partnership.

In 2008 when President Barack Obama won the election, he held phone talks with then South Korean President Lee Myung-bak two days after the election. (Yonhap)