Relief workers awaited a delayed U.N. airlift of blankets, food and medicine Thursday in the besieged capital of Kabul, where a rebel rocket attack that killed seven people and wounded 21 others put even more pressure on the embattled government.

U.N. officials said they expected the shipment of emergency relief supplies to be flown Thursday to Kabul from the Pakistani capital of Islamabad after a two-day delay attributed to undisclosed security concerns.A U.N. spokesman in Islamabad said Wednesday 32 tons of blankets, food and medicine, needed in Kabul because of a blockade by U.S.-backed rebels and the coldest winter in 16 years, would be carried aboard an Ethiopian Airlines plane.

In Kabul, a U.N. official said he was "90 percent sure" the supplies would arrive Thursday in the capital, where a rebel rocket attack Wednesday added to the worries of the government and the city's 2 million residents.

Kabul Radio, monitored in Pakistan, said seven people were killed and 21 wounded in a rocket attack.

The attack came a day after a guerrilla leader said in published remarks the rebels would enforce their blockade on Kabul rather than mount a direct attack that could leave civilian casualties.

Western diplomats say the guerrillas have refrained since November from staging major rocket attacks against Kabul to allow Soviet forces to withdraw unhindered.

Officials said about 300 Soviet soldiers protecting the Kabul airport and a Soviet food airlift will stay at their post until about Monday, two days before a U.N.-mediated deadline for Moscow's troop pullout from Afghanistan.

The Soviet pullout leaves Afghan President Najibullah's government vulnerable to the U.S.-armed Afghan rebels determined to overthrow the regime.

With a week left for the Soviet withdrawal, reporters were taken Wednesday to a section of the Kabul airport still under Soviet control to monitor arrivals of Soviet planes bringing food.

Moscow says it plans to continue to the airlift even after the troop withdrawal.

Under a U.N.-mediated accord signed in Geneva last year, the Soviet Union agreed to withdraw all its 103,000 troops from Afghanistan by next Wednesday. The Soviets invaded Afghanistan in 1979 to prop up a communist regime beset by internal discord and Moslem guerrillas.