Trump's comments came on his second day in the region, where Trump hopes to reaffirm his tough stance on North Korea and rally allies to endorse his strategy.
The two leaders also discussed the lingering issue of Japanese citizens abducted by North Korea.
Trump and Abe then walked along red carpets laid out across the cobblestones to approach the military band.
President Donald Trump's first trip to Asia began with a round of golf, a custom cap and a hamburger of American beef.
Soon after Trump's arrival in Tokyo Sunday, he and Abe played nine holes at Kasumigaseki Country Club, the planned site of the 2020 Olympics golf tournament.
"It's a lot of jobs for us and a lot of safety for Japan", he said at the news conference, which followed a bilateral meeting with Abe in which the two leaders in which they professed to be "100 together" when it comes to the response to North Korea.
"Right now our trade with Japan is not fair and it isn't open", Trump told business leaders in Tokyo Monday.
According to sources, Abe later said to people close to him, "It's important to show such relations to the rest of the world".
On his way to Japan, Trump told reporters aboard Air Force One that during his Asia trip he expected to meet Russian President Vladimir Putin. He also aims to increase Japan's diplomatic and security presence.
On trade, Trump took what he could get, even if he is largely leaving Japan empty-handed.
Trump has rattled some USA allies with his vow to "totally destroy" North Korea if it threatens the United States, for deriding Kim as a "Rocket Man on a suicide mission" and for dismissing as pointless any diplomatic engagement with Pyongyang.
Abe, who has taken a more hawkish view on North Korea than some of his predecessors, agreed with Trump's assessment that "all options are on the table" when dealing with Kim Jong Un and announced new sanctions against several dozen North Korea individuals.
Kim, who has also made clear he has little interest in negotiations, at least until North Korea develops a nuclear-tipped missile capable of hitting the United States, has called Trump a "mentally deranged USA dotard".
Bickering erupted between ruling and opposition party lawmakers during the committee's meeting as opposition members denounced South Korea's recent pledges made in the agreement with China. There is concern within the government and the ruling parties about Abe's excessive inclination toward Trump.
Trump also said Washington wants to make the United States the most attractive place to hire, invest and grow.
The president spoke of the "enduring bond" between the US and Japan and said the most important area of cooperation was in countering "the unsafe aggressions of the regime in North Korea".
South Korea now pays more than 900 billion won ($800 million) annually and negotiations with the United States are to start in the coming months to try to determine a new amount for South Korea to contribute.
"Japan's No. 1 priority is still keeping the US from talking about foreign exchange", Yuichi Kodama, chief economist at Meiji Yasuda Life Insurance Co.in Tokyo was quoted as saying on the matter.
As part of a welcoming ceremony, President Trump stopped with Japanese Premier Shinzo Abe to feed the koi fish at a pond on the grounds of the Akasaka palace in Tokyo.
Mr Abe will be looking for a united front against North Korea and reassurances that the USA will stand by its treaty obligations to defend Japan if attacked.