His comments came shortly before the Saudi-led military coalition fighting Shiite rebels in Yemen announced it would reopen Sanaa airport and the port of Hodeida on Thursday for urgent humanitarian aid and United Nations aircraft.
The International Rescue Committee says a partial reopening of ports will ease the flow of humanitarian aid, but "will still leave the population of Yemen in a worse situation than they were two weeks ago before the blockade started".
United Nations officials welcomed the move, albeit cautiously, as it was not clear whether humanitarian missions into Yemen would be allowed to return to pre-blockade levels. It did not specify when or if it would ease a blockade on commercial traffic.
Haq said the U.N.is "monitoring these developments and we're trying to see whether that actually takes place on the ground". "Of course, if that were to happen that would be a very welcome and critically important development".
The NRC says while the action for humanitarian aid represents a glimmer of hope in the countdown towards starvation in Yemen, it is still a minor and insufficient concession within a blockade that is causing the suffering of millions of Yemeni people. "Millions of Yemenis need urgent access to lifesaving food, fuel and medicines than can be delivered by humanitarian agencies ready to assist if allowed".
The UN says a continuation of the two-week blockade would make Yemen's war-battered population more vulnerable to cholera and starvation.
"It is good news, but we are still waiting to see the specific details", Jamie McGoldrick, the UN's humanitarian chief for Yemen, said.
The coalition had closed all air, land and sea access to Yemen earlier this month following the launch of a missile fired toward the Saudi capital.
Allied with Yemeni strongman Ali Abdullah Saleh, the Iran-backed Huthi rebels control the capital Sanaa along with much of northern Yemen.
Reopening the ports to aid but not to commercial imports is pitiful bartering with peoples lives.
Saudi Arabia said the move was meant to stop the flow of arms to the Houthis from Iran, although Iran has denied supplying weapons to the rebel forces.
In 2015, Saudi Arabia and its allies joined the Yemeni government's fight against the rebels.