(CNN) US national security adviser John Bolton has canceled his trip to South Korea next week, even as preparations ramp up for a second summit between President Donald Trump and North Korean leader Kim Jong Un.

"Ambassador Bolton has canceled his travel to the Republic of Korea to focus on events in Venezuela," National Security Council spokesman Garrett Marquis said in a statement. Bolton is still planning to travel to Hanoi, Vietnam, with President Trump for the North Korea summit, which starts February 27, he said.

Bolton, who famously flashed reporters a yellow notepad with the scrawled words "5,000 troops to Colombia" during a briefing about Venezuela last month, won't be the only high-ranking US official focusing on the divided, oil-rich country.

Monday, US Vice President Mike Pence is expected to travel to Colombia in an effort to pressure embattled Venezuelan President Nicolas Maduro to step down. He plans to meet with the Lima Group, a regional bloc of nations, and deliver remarks to address the "tragic humanitarian and security crises unfolding in Venezuela and ongoing US efforts to deliver aid to the country."

And Elliott Abrams, the recently appointed US Special Representative for Venezuela, arrived in the Colombian border town of Cucuta Thursday.

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