Trump's announcement contradicted his own aides on Monday who said that "cutting payroll taxes is not something under consideration at this time''.
Trump made the remarks in a 22-minute speech at the national assembly, South Korea's parliament.
Trump said in late April that Singapore and the Demilitarized Zone on the Korean Peninsula could be where he would meet with Kim, but on Wednesday he ruled out the Demilitarized Zone.
Tsai Ing-wen, the leader of Taiwan's ruling Democratic Progressive Party, refused to recognize the one-China principle as she started her second term as Taiwan leader last week.
Trump's threat on Monday of a military option in response to the alleged attack further strained ties with Russia, endangering the "de-escalation zone" and hotlines the two sides have agreed to set up so as to avoid conflicts on the Syrian battleground.
Trump said he expected to carry out cooperation with Xi and continue in depth talks on the next day.
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Trump said on Aug 20 that he would "most likely" meet with top DPRK leader Kim Jong-un for a second time, and he believed Pyongyang had taken specific steps toward denuclearization.
Trump's warning came hours after the Iraqi parliament on Sunday passed a draft law requiring the government to end the presence of foreign forces in Iraq, and prevent them from using Iraqi air, space and water.
Trump also met with Japanese Prime Minister Shinzo Abe on Friday. They reviewed the recent developments related to the DPRK and discussed how best to work with the international community, including South Korea, to continue to put pressure on the DPRK until it implements its commitment to denuclearize.
Trump, who has made a hardline immigration stance a key issue of his presidency and 2020 re-election bid, postponed the operation last month after the date was leaked, but on Monday he said it would take place after July 4.