Fifteen Western nations agreed tonight to allow Poland to delay repayment of a large chunk of imediate debts to help relieve its stricken economy.

Polish Finance Minister Marian Krzak told reporters that the decision "brings us nearer to the light" in the effort to deal with a severe economic emergency that has had repercussions in the country's political situation and its relations with the Soviet Union.

Krzak also said that the long-sought agreement by the 15 governments gave Warsaw a good basis on which to work in seeking similar debt rescheduling from private banks.

The agreement today to "reachedule" -- delay repayment -- of some $2.6 billion in official debt to Western governments falling due during the rest of this year provides Poland with the first big chunk of a $10 billion aid package it requested last month from Western governments and banks to help it solve its severe financial crisis.

Poland has told governments and bankers that meeting its financial emergency is crucial to its attempts to satisfy internal demands for economic and other reforms without risking armed Soviet intervention.

u.S. sources said in Washington that "the fact that the agreement has been concluded so quickly, given its complexity and the amount of money involved, is quite a success for Poland" and that it should "have a very positive effect" on Poland's efforts to get banks to reschedule payments. "I suspect the banks may very quickly follow up with an agreement of their own," one source said.

[According to the U.S. sources, the 15 countries agreed to reschedule 90 percent of Poland's official debt due this year, after tentatively agreeing earlier this month to reschedule only 80 percent. The Unted States, citing similar action to revive Turkey's economy, reportedly pressed initially reluctant Western European governments to accept the 90 percent figure.]

Amid warnings that its economic crisis was deepening, Poland had asked the Western governments to reschedule a large portion of its official debt by the end of this month.

Krzak told reporters at the signing ceremony in the French Treasury that the agreement was a small but significant step in the development of Poland's cooperation with the West.

"Poland is in a difficult period, and as the prime minister said recently we were in a dark tunnel. This agreement brings us nearer the light," Krzak said. "We are determined to do everything we can to improve our economy and improve cooperation with the West."

At paralle but separate talks in London, Poland has been urging Western bankers to refinance some $3.1 billion in commercial debts due for repayment this year.

Charles Meissner, the U.S. negotiator, said the rescheduling would help Poland finance about 25 percent of its 1981 current-account deficit. He said Poland has received assurances of $2.5 billion in additional credits from Western nations this year.

Poland still will have a current account payments shortfall of some $2 billion even if it manages to renegotiate the terms of debts maturing this year with Western commercial banks, Meissner said. Poland reportedly will need financial assistance this year merely for imports of food and basic materials.

Sources here estimate Poland's total foreign debts at about $26 billion, about 40 percent of which is official, or government-backed, and the remaining owed to private banks.

The 15 countries represented at today's talks were the United States, Japan, West Germany, France, Britain, Italy, Canada, Austria, Belgium, Denmark, Finland, the Netherlands, Norway, Sweden and Switzerland.