By Ju-min Park and Heekyong Yang
SEOUL (Reuters) - Just over three months in office, South Korea's president is finding little room to maneuver between old enemy North Korea and increasing combativeness from long-time ally, the United States.
North Korea has snubbed offers for talks from President Moon Jae-in, the South's first liberal leader in a decade. And U.S. President Donald Trump has alarmed Seoul with his warnings that the United States will unleash "fire and fury" if threatened by North Korea's nuclear and missile programs.
Any confrontation between the two will inevitably draw in South Korea, which faces thousands of North Korean troops and artillery guns across the heavily militarized border.
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With few options at his command, Moon has been encouraging Washington to talk directly to Pyongyang to resolve differences, according to senior officials and advisers to the president.
"Dialogue is urgently needed to stop the North from developing its weapons programs further," said Moon Chung-in, a special adviser to the president on foreign affairs and national security.
"But North Korea sees the South as powerless and won't negotiate with us. They want to have direct talks with the United States," said Moon, who also holds the post of distinguished professor at Yonsei University in Seoul.
Washington is insistent on maximizing economic sanctions and keeping up pressure on the North to stop its pursuit of nuclear weapons.
"Moon has been telling Trump that a military option should never be considered, but there is not much we can do when two strong leaders (of North Korea and the United States) are clashing," said Lee Su-hoon, who headed a group of national security advisers for the president until July.
"But no one wants a catastrophic end. Down the road, I expect there will be a compromise and dialogue."
In comments on Monday, President Moon insisted on dialogue to resolve differences with the North, "whatever ups and downs we face".
"I am certain the United States will respond to the current situation calmly and responsibly in a stance that is equal to ours," he said in opening remarks at a meeting with senior aides.
But there seems little likelihood of dialogue at this point.
In his most recent phone conversation with Trump a week ago, Moon said "a tragic war should never happen on the Korean peninsula," according to his presidential spokesman. But within days, Trump warned Pyongyang would meet fire and fury if it threatened the United States.
The sharp rise in tensions is expected to dominate a speech by Moon on Tuesday to commemorate the 72th anniversary of liberation from Japanese colonial rule. He also holds a news conference on Thursday to mark his 100th day in office.
The anniversary is shared by North Korea and its leader Kim Jong Un may also make a speech.
Tensions between North Korea and the United States surged last week after the isolated country said it would finalize a plan by mid-August to launch four intermediate range missiles toward waters off the U.S. Pacific territory of Guam.
Referring to Kim Jong Un, Trump said: "If he does anything with respect to Guam or any place else that's an American territory or an American ally, he will truly regret it, and he will regret it fast."
The heated rhetoric has raised fears of a sudden clash, that once started could cause massive casualties in the South's densely populated capital Seoul, which is just 40 km (25 miles) south of the border. The Seoul metropolitan area is home to 25 million people.
Moon, closely linked with South Korea's 1998-2008 policies of engaging with the North, came to office promising to revive ties with Pyongyang.
He filled his national security team with several key players of that time, naming them to the posts of prime minister, spy chief and unification minister.
"The problem is that Kim Jong Un is nothing like his father," said Nam Seong-wook, professor of North Korea Studies at Korea University in Seoul.
"Officials in the Moon government don't know him, since they just have dealt with Kim Jong Il," Nam said, referring to the current leader's father, who died in late 2011.
Less than six years into his reign, Kim has tested more missiles than his father and grandfather combined, conducted three nuclear tests, and is racing to develop a nuclear-tipped missile that can hit the U.S. mainland.
Faced with this aggressiveness, and Kim's refusal to talk to the South, Seoul has few options, analysts said.
"At this point, there's little South Korea can do but... communications with the United States and China, and we're doing a good job at that," said Lee, Moon's former adviser.
(Additional reporting by Jane Chung and Haejin Choi, Editing by Soyoung Kim and Raju Gopalakrishnan)