SANAA, Feb. 11 (Xinhua) -- Visiting UN Special Envoy to Yemen Martin Griffiths warned on Monday that the grain aid stored in the besieged Hodeidah city to feed over 3 million people is "at risk of rotting."

"The urgency of UN access to the Red Sea Mills in Hodeidah is growing by the day," Griffiths said in a joint statement with the UN Humanitarian Chief Mark Lowcock.

"The World Food Programme's grain stored in the mills, which was enough to feed 3.7 million people for a month, has been inaccessible for over five months and is at risk of rotting," they said in the statement.

"We are encouraged by recent engagement of all (Yemeni rival) sides, working with the UN on the ground, to create the necessary conditions for the team to reach the mills without further delay," they added.

Hodeidah is the lifeline of Yemen's most commercial imports and humanitarian aid. The four-year civil war has pushed over 12 million people to the verge of starvation and created what the UN calls the world's worst humanitarian crisis.

The warring parties reached a peace deal in Stockholm in December last year. They have largely held the cease-fire deal in Hodeidah but failed to withdraw their forces.

The rebels continue to fortify themselves inside the city while the government troops have been massing in the southern and eastern outskirts.

Last week's negotiations led by Michael Anker Lollesgaard, head of the UN cease-fire monitor team in Hodeidah, resulted in what the UN called a "preliminary deal", yet the warring parties hotly disputed over it.