WASHINGTON -- US Defense Secretary Jim Mattis said Wednesday that efforts to denuclearize North Korea remain "firmly in the diplomatic lane," with military options as a backup.

Talk of a limited military strike on North Korea gained traction last week after it was reported that US President Donald Trump's initial pick for ambassador to Seoul was dropped over his objections to the so-called "bloody nose" strategy.

Mattis was asked during a White House press briefing whether he thinks the chances of war with Pyongyang have increased since the Trump administration took office a year ago.

"As far as the situation with Korea, it is firmly in the diplomatic lane," he said. "And we, of course, back up Secretary of State (Rex) Tillerson's foreign policy efforts, as guided by the president, with viable military options."

The focus on diplomacy was clearly demonstrated by the UN Security Council's unanimous adoption of three sanctions resolutions against Pyongyang last year, he added.

The sanctions were imposed in response to North Korea's three intercontinental ballistic missile tests and its sixth and most powerful nuclear test.

On Friday, the communist nation will send a high-level delegation to the opening of the PyeongChang Winter Olympics, including the younger sister of North Korean leader Kim Jong-un.

The US delegation will be led by Vice President Mike Pence, feeding speculation the two sides could meet on the sidelines.

Asked whether he supports that kind of contact, Mattis said, "Vice President Pence is quite capable of making the call on that there while he's in Korea." (Yonhap)