Pan birdied two of his first nine holes to lie joint third at level par midway through the weather-delayed second round while Kim was a further stroke back, after covering his first 11 holes in two under.
Both players will aim to stay in contention for the year's second Major championship when they return to Merion Golf Club's challenging East Course on Saturday to resume at 7:15am.
"I'm really happy with my performance," Pan, 21, said after covering the outward nine in two-under during a round where the average score in the 155-strong field was almost five over par.
"Two under, that's a good score for me and I'm very satisfied with my performance this afternoon. But it's still early in the tournament. Two more days, and I've got 45 holes to go."
Asked if he felt any pressure challenging for the Major widely regarded as the most gruelling to win, Pan replied: "Actually I'm very excited to see my name on the leaderboard.
"The reason I don't feel pressure is because the holes are hard and I am just trying every shot hard."
Pan is making his second appearance in a US Open, having missed the cut in last year's championship at the brutally difficult Olympic Club outside San Francisco, and he relishes the Major environment.
"This atmosphere here is great," said the Taiwanese, who at the age of 15 in 2007 became the youngest player to reach the quarter-finals of the US Amateur since Bobby Jones.
"I came to the US Open 2011 and I just fell in love with this kind of atmosphere. I feel I belong to that kind of place.
"I'm not saying I'm good enough, but I love this kind of feeling and the competition is great. I just want to be here always."
Kim, who earned a US Open spot for the first time after making two birdies in his last three holes in sectional qualifying, made a promising start to Friday's second round after teeing off at the par-four 11th.
He offset a bogey at the par-four 14th with a birdie on 16 to cover Merion's difficult closing stretch in level par, then edged up the leaderboard with further birdies at the first and second before play was suspended for the day in fading light.
"I got off to a pretty solid start, parred the first few holes and I definitely could have made birdie on all of them," the 19-year-old said.
"And then I hit a poor drive on 14 and made a bogey.
"But I made a really good birdie on 16, and kind of came back. I just tried to get through that 14-through-18 stretch in even par, because then you're making up shots on the field."
Asked what his expectations were heading into the weekend on a layout known for its thick rough and narrow fairways and now running faster and firmer, Kim replied: "I'm not sure.
"Trying not to think about it too much. Low expectations and whatever happens, happens tomorrow."
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