The United States has "many" military options against North Korea, including some that do not put Seoul at risk, Defense Secretary Jim Mattis has said.
His comments come after President Donald Trump's administration ramped up pressure on North Korea, warning Pyongyang will be "destroyed" if it refuses to end its "reckless" nuclear and ballistic missile drive.
"There are many military options, in concert with our allies, that we will take to defend our allies and our own interests," Mr Mattis told Pentagon reporters.
He did not provide details, but he responded affirmatively when asked if these included options that would not put Seoul at grave risk.
Mr Mattis also confirmed that the US and South Korea had discussed the option of sending limited-size "tactical" nuclear weapons to South Korea.
North Korea's weapons drive is set to dominate Mr Trump's address to the United Nations General Assembly tomorrow and his meetings with South Korean and Japanese leaders this week.
Tensions flared when Kim Jong-Un's regime tested what it termed a hydrogen bomb many times more powerful than its previous device.
The North also fired a ballistic missile over Japan and into the Pacific on Friday, responding to fresh new UN sanctions with what appeared to be its longest-ever missile flight.
Amid calls for the United States and Japan to shoot down such missiles, Mattis said there was no need to do so because they were not a direct threat.
"The bottom line is that in the missiles, were they to be a threat, whether it be the US territory Guam, obviously Japan, Japan's territory, that would elicit a different response from us," he said.
Meanwhile the US and Chinese leaders have committed to "maximising pressure on North Korea," the White House has said.
Mr Trump and his Chinese counterpart Xi Jinping discussed "North Korea's continued defiance of the international community and its efforts to destabilize Northeast Asia" by phone, the White House said.
"The two leaders committed to maximising pressure on North Korea through vigorous enforcement of United Nations Security Council resolutions."
Mr Trump is currently in New York for the United Nations General Assembly but Mr Xi - who has a major Communist Party congress that will cement his leadership for the next five years - is not attending the event.
Mr Trump is expected to make his first presidential visit to China in early November.
September has seen a significant ratcheting up of already sky-high tensions with North Korea.
Already North Korea has conducted its sixth and most powerful nuclear test and staged an intermediate-range missile test over Japan.
The UN Security Council last week imposed a fresh set of sanctions, though the United States toned down its original proposals to secure support from China and Russia.
The US president has not ruled out a military option, which could leave millions of people in the South Korean capital - and 28,500 US soldiers stationed in the South - vulnerable to potential retaliatory attack.
The US flew four F-35B stealth fighter jets and two B-1B bombers over the Korean peninsula today in a blunt show of force.
China's official news agency, Xinhua, said that during the phone conversation "Xi also expressed sympathy and solicitude to Trump and the American people for the hurricane attacks on the United States over the past few days."
"The two leaders also exchanged views on the current situation on the Korean Peninsula."
