U.S. White House Press Secretary Sarah Huckabee Sanders listens to Health and Human Services Secretary Alex Azar answer questions from the news media during the daily briefing at the White House in Washington, U.S., May 11, 2018. REUTERS/Leah Millis

WASHINGTON (Reuters) - The United States is still hopeful about a planned summit with North Korean leader Kim Jong Un but President Donald Trump is prepared for a tough negotiation process, White House spokeswoman Sarah Sanders said on Wednesday.

North Korea threw next month’s summit between Kim and Trump into doubt on Wednesday, threatening weeks of diplomatic progress by saying it may reconsider if Washington insists it unilaterally gives up its nuclear weapons.

“We’re still hopeful that the meeting will take place and we’ll continue down that path but at the same time we’ve been prepared that these could be tough negotiations,” Sanders said in an interview with Fox News.

“The president is ready if the meeting takes place. If it doesn’t, we’ll continue the maximum pressure campaign that’s been ongoing.”

Sanders said the comments from North Korea were “not something that is out of the ordinary in these types of operations.”

“The president’s fully prepared and fully ready to carry on in these conversations both leading up to and if the meeting takes place,” she said. “He’ll be there and he’ll be ready.”

According to North Korea’s official KCNA news agency, Pyongyang’s first vice minister of foreign affairs, Kim Kye Gwan, specifically criticized U.S. national security adviser John Bolton, who has called for the North to quickly give up its nuclear arsenal in a deal that mirrors Libya’s abandonment of its weapons of mass destruction.

Sanders played down those concerns. “I haven’t seen that as part of any discussions so I’m not aware that that’s a model that we’re using,” she told reporters at the White House on Wednesday.

The Trump-Kim meeting is scheduled for June 12 in Singapore.