SEOUL (Reuters) - South Korea and the U.S. will reach agreement on sharing the cost of U.S. troops in the country if Donald Trump is elected president, even though he is likely to pressure Europe to increase defence spending, a former Trump security adviser said.

During his first presidency Trump accused Seoul of "free-riding" on U.S. military might, with more than 28,000 American troops stationed in South Korea as part of efforts to deter its nuclear-armed neighbour North Korea.

The allies are in talks for a new U.S. troop deal, so-called 12th Special Measures Agreement (SMA), to take effect in 2026. South Korean media has said the aim was for an agreement before the November U.S. presidential election.

"I think that the SMA talks will continue and will reach a settlement that both sides will be content with, when Trump comes to office," Fred Fleitz, a senior National Security Council official during the Trump administration, said in Seoul on Tuesday.

Fleitz said he believed if Trump was elected he would likely pressure European allies to spend more on defence, but not South Korea, citing the "current environment of increased threats from North Korea, from China" as a reason.

Fleitz, who is visiting Seoul for meetings with South Korean researchers and officials including a vice foreign minister, said he was not speaking for Trump and instead offering his own assessment.

Another round of SMA negotiations is set to take place this week in Seoul, according to South Korea's foreign ministry.

Fleitz, vice chair at the America First Policy Institute, a U.S. thinktank, also said he believed Trump would try to meet North Korean leader Kim Jong Un again in his second presidency.

"I think that the Trump administration has to re-engage Kim," he said, expecting "intensive consultations with Japan and South Korea, probably Taiwan among U.S. allies", to come before a meeting with the North's leader.

Between 2018 and 2019, Trump and Kim met three times in what yielded powerful images but few concrete steps for North Korea's denuclearisation.

His advice for the potential Trump-Kim meeting should be on conditions that North Korea should stop supplying weapons to Russia, Fleitz added.

"I think there will be tough policies against China and North Korea. But I also think there will be dialogue," he said.

(Reporting by Ju-min Park; Editing by Michael Perry)

By Ju-min Park and Heekyong Yang