The North Korea meeting will be followed by one of the so-called "Quad" - the United States plus France, Britain and Germany, the Western partners who, with Russian Federation and China, signed the 2015 Iran nuclear deal.
"The day we will finish this war against ISIS, if we leave, definitely and totally, even from a political point of view, we will leave the floor to the Iranian regime, Bashar al-Assad and his guys, and they will prepare the new war", he said on "Fox News Sunday", using an alternative acronym for the Islamic State militant group.
Trump is also working on his own landmark meeting with the North Korean leader in the coming weeks, after dispatching CIA Director Mike Pompeo on a secret mission to meet with Kim two weeks ago to set the table.
"All of us women foreign ministers said we are often in meetings where we are the only woman, and so Taro got a little bit what it was like", she joked, thanking him.
But, while the Western allies appeared united in their resolve to face down Russian Federation, the European partners remain concerned that Trump may tear up the 2015 Iran nuclear deal next month.
The G7 has also blamed Russia for a nerve-agent attack on a former Russian double agent and his daughter last month in Britain.
Freeland will be joined Monday by Public Safety Minister Ralph Goodale, who will lead his G7 interior minister counterparts in talks on terrorism and cyber security.
The meetings are not expected to discuss further punitive measures against Moscow because Britain, France, Germany and Italy are members of the 28-nation European Union, which must agree collectively on what steps to take, said two diplomats briefed on the meeting. Neither official spoke to reporters as the talks began.
In other areas, the foreign ministers meeting is expected to focus on USA complaints about Iran's influence in the Mideast and its nuclear program as well as ways to pressure Russian Federation over conflicts in Syria and Ukraine.
US President Donald Trump has called the 2015 Iran pact one of the worst agreements ever negotiated and will decide by May 12 whether to restore US economic sanctions on Tehran, which would be a severe blow to the pact.
Iran says its nuclear programme is only for peaceful purposes.
Iranian President Hassan Rouhani said on Saturday Iran's atomic agency was ready with "expected and unexpected" reactions if the USA pulled out of the 2015 agreement.
As the pair sat down in the office of the chancellor of the University of Toronto, Johnson was heard telling his U.S. counterpart "one of the things we are concerned about now is the JCPOA and where that is headed".
Pyongyang said on Saturday it would suspend nuclear and missile tests and scrap its nuclear test site.
The U.S. ambassador to Canada said Sunday that President Donald Trump is leading worldwide efforts to persuade North Korea to give up its nuclear weapons.