Mr Guterres' appeal comes hours after Houthi rebels in Yemen launched a missile towards a heavily populated Saudi Arabian city, which failed to cross the border, according to the Arab Coalition forces.
The United Nations asked donors on Tuesday for almost $3 billion to help an estimated 13 million people who urgently need aid in war-ravaged Yemen. Twenty-two million people - three-quarters of the population - require some form of humanitarian assistance.
The humanitarian situation in Yemen is considered the worst in the world.
A Saudi oil tanker was targeted by the Iran-aligned Houthi movement on Tuesday afternoon local time off Yemen's port of Hodeidah, sustaining minor damages and completing its course north, Saudi-owned Al Arabiya reported, citing the Arab coalition that is fighting the Houthis in Yemen.
During the event, Sweden and Switzerland organized a panel discussion on humanitarian access in Yemen based on the Presidential Statement of the UN Security Council adopted on March 15.
"We all know that there is a war".
United Nations launches $3bn Yemen funding drive
"Independent of the fact that there is a war, there are humanitarian obligations that are assumed by countries", he said. "But with worldwide support, we can and must prevent this country from becoming a long-term tragedy", he said. He also stressed the Kingdom's efforts to find a political solution to the Yemeni crisis and provide humanitarian relief and support to its people. "The solution has always been political".
The UN s Yemen envoy, Martin Griffiths, has recently visited Riyadh and Sanaa in hopes of revitalising sputtering peace talks.
The Saudi-led coalition shut down the country s land, sea and air borders past year in response to a missile attack by the Huthis that was intercepted near Riyadh.
While the coalition has eased the blockade, restrictions on deliveries persist.
Noting that all ports must remain open to humanitarian and commercial cargo, the medicines, food and the fuel, Guterres said: "Humanitarians must be able to reach the people who need help the most, without conditions".
Chinese Space station plummeting to Earth
On this mission, the crew spent 11 days at the station and completed two dockings - one computer-controlled and one crew-guided. You can also follow ESA's Twitter account for the latest updates on estimated time and location of the space station's reentry.