Often called the "forgotten war" amid Western media focus on Syria, Yemen's situation is now catastrophic, with "nearly half of all children aged between six months and 5 years old chronically malnourished", according to Guterres.
The UN called the incident "one of the deadliest attacks on children since the conflict in Yemen escalated in March 2015".
"We all know that there is a war".
The funding brings the total US humanitarian assistance for the war-torn country to over $854 million since 2017.
"This pledging conference represents a remarkable success of global solidarity to the people of Yemen", Guterres said.
The UN has said that three-quarters of Yemen's population - about 22 million people - need some form of aid.
The Iran-backed Houthi militias in Yemen fired on Monday a rocket towards Saudi Arabia, but it failed in reaching its target.
Ex-spy poisoning row: Britain unable to identify source of nerve agent
There are doubts that rogue agents could have carried out the attack without approval from the top levels of Russian government. Vladimir Putin won the Russian election last month by a landslide to give him a record fifth term as president.
"While these contributions will provide some immediate relief, no amount of humanitarian or development assistance will end this conflict and the suffering of millions", the agency acknowledged. "The solution has always been political".
Griffiths has already held talks with both sides in the war, which has drawn in regional powers, meeting Houthi authorities who hold the capital Sanaa as well as internationally-recognised Yemeni President Abed Rabbo Mansour Hadi and Saudi officials in Riyadh.
"I believe there is an opportunity and that opportunity must be seized", Guterres said, explaining that Griffiths was "encouraged" by his trip and sees a window for further talks.
The 2018 Humanitarian Response Plan for Yemen requires $2.96 billion to reach more than 13 million people across the country.
In November 2017, Saudi Arabia announced that it was shutting down Yemen's air, sea, and land borders.
Guterres told the conference: "All ports must remain open to humanitarian and commercial cargo, the medicines, food and the fuel needed to deliver them".
Worldwide donors have pledged more than $2bn in humanitarian aid to provide life-saving assistance and protection to the people of Yemen bearing the brunt of a deadly conflict now its fourth year.
In November 2017, the Saudi-led coalition eased a three-week-long blockade on rebel-held parts of Yemen, following an global outcry.