G8 foreign ministers including US Secretary of State John Kerry held a second day of talks in London on Thursday with the crisis on the Korean peninsula and the Syrian conflict topping the agenda.
After a dinner late Wednesday, the ministers from the Group of Eight industrialised nations held formal talks on Thursday likely to be dominated by North Korea's expected missile launch.
Kerry has already met with his Russian and Japanese counterparts to discuss the crisis, in which US Defence Secretary Chuck Hagel warned Pyongyang was "skating very close to a dangerous line".
The secretive communist state has threatened nuclear strikes against the United States and South Korea, and observers are expecting a missile launch at any time.
Foreign Minister Sergei Lavrov of Russia, which maintains close ties to North Korea's key ally China, warned after talks with Kerry on Wednesday against exacerbating tensions with military manoeuvres.
While stressing that Russia and the United States had "no differences" on North Korea, Lavrov said: "One just shouldn't scare anyone with military manoeuvres and there's a chance that everything will calm down."
Kerry also held talks late Wednesday with Japanese Foreign Minister Fumio Kishida, where they discussed China's role and how to "change the dynamic" in North Korea, according to a US State Department official.
The US Secretary of State, who will visit South Korea on Friday, "emphasised the importance of continuing to put pressure on North Korea with economic sanctions", the official said.
The ministers from the Group of Eight industrialised nations will also discuss the conflict in Syria, which is now in its third year and has claimed 70,000 lives, according to the United Nations.
Kerry met with members of the Syrian opposition on Wednesday, where they renewed their appeal for weapons to aid their fight against President Bashar al-Assad's regime.
But a top State Department official said Kerry "didn't promise anything" at the lunch, which was hosted by British Foreign Secretary William Hague.
"We are always considering a variety of options, we are going to continue to aid the opposition, working with them in terms of what they need, in terms of what we're willing to provide," the US official said.
The US and EU are currently providing non-lethal aid such as communications equipment, and are beginning to distribute food and medical supplies to the Free Syrian Army, but have stopped short of providing weaponry.
Britain has been pushing to amend an EU embargo blocking the supply of arms to the rebels, but there are concerns that any weapons supplied may fall into the wrong hands.
This fear was exacerbated by the declaration by one of the top rebel fighting forces in Syria, the Al-Nusra Front, of its allegiance tp Al-Qaeda chief Ayman al-Zawahiri.
Russia is strongly opposed to any attempt to arm the rebels and, as a key ally of Assad, has repeatedly blocked UN Security Council efforts to increase pressure on the Syrian president.
Kerry and Lavrov discussed the crisis during their talks on Wednesday in a bid to find common ground.
Hague later called the talks with the Syrian opposition "very productive" and stressed the Syrian coalition's executive arm "will have a vital role to play in delivering governance, services and support to the Syrian people".
US officials confirmed that the "Friends of Syria", a group opposed to Assad's rule comprising the United States, European and Arab countries, will hold its next meeting in Istanbul on April 20, and Kerry will be among those attending.
Another issue on the table in London is Iran, which this week unveiled a new uranium production facility and two extraction mines only days after talks with world powers on its disputed nuclear programme ended in deadlock.
"They have continued to move forward, we are very concerned about what they are doing," a senior State Department official said, asking to remain anonymous.
"We weren't blindsided about it, because we are rarely blindsided about the things that they are considering. But they did not specify that they were going to do this," the official said.
The Group of Eight rich nations are Britain, Canada, France, Germany, Italy, Japan, Russia and the United States.
Britain, which holds the rotating chairmanship of the group this year, will host a leaders' summit in Northern Ireland in June.