WARSAW, Poland (AP) _ The Soviet foreign minister pledged Tuesday on his first visit to the new Solidarity government to maintain key fuel supplies, and Prime Minister Tadeusz Mazowiecki said he will travel next month to Moscow.

In addition, Foreign Minister Eduard A. Shevardnadze said the Soviet Union will try to uncover the truth about the World War II massacre of thousands of Polish officers at Katyn. The issue has long been a sore point in Polish- Soviet relations.

Upon arrival at Warsaw's Okecie airport, Shevardnadze said, ''The Soviet leadership places a lot of importance'' on his visit to Warsaw.

He was met by Polish Foreign Minister Krzysztof Skubiszewski, a professor of international law and Solidarity sympathizer, who told Shevardnadze: ''This is an important visit for us. We have high expectations for it.''

They held two rounds of talks before Shevardnadze went to the Council of Ministers to meet Mazowiecki, a former Solidarity editor who became the first non-communist to lead an East bloc government on Aug. 24.

''I am very happy about our many-faceted talk,'' Mazowiecki said after his two-hour meeting with Shevardnadze. ''I accepted the invitation to Moscow with gratitude,'' and said he expected to leave for the Soviet Union on Nov. 23.

Polish officials say the important items on the agenda with the Soviet Union were restructuring economic relations between Warsaw and Moscow as part of a drive to create a market economy, resolution of historical ''blank spots'' and easing of contacts between Polish and Soviet citizens.

''There are some problems, but they were discussed in the spirit of understanding and seeking solutions,'' Foreign Ministry spokesman Stefan Staniszewski said after the meeting, which he said focused on economic problems and new forms of cooperation.

Shevardnadze will meet with Polish officials again Wednesday before holding discussions Thursday and Friday in Warsaw with Warsaw Pact foreign ministers.

According to Staniszewski, Shevardnadze pledged the Soviet Union would maintain its level of deliveries to Poland, which is dependent on Moscow for oil, gas, electricity and raw materials.

It was a significant gesture of good will because Poland has been having trouble delivering products to the Soviet Union due to its protracted economic crisis, which includes a shotage of industrial goods, high inflation and a $39 billion foreign debt.

Poland has said it wants to renegotiate its contracts with its trading partners in the Soviet-led Comecon alliance to make them more market-oriented.

Shevardnadze is the highest-ranking Soviet official to visit Warsaw since Mazowiecki's election. Two days after Mazowiecki took office, KGB chief Viktor Kryuchkov met with him and called him a ''solid man.''

The Soviet decision not to interfere in the assumption of power by a Solidarity government, relayed by President Mikhail S. Gorbachev in a telephone call to Polish Communist First Secretary Mieczyslaw F. Rakowski on Aug. 22, marked a significant departure from Soviet treatment of its East bloc allies.

Shevardnadze underlined this point Monday in a major foreign policy speech in Moscow, saying that as Warsaw Pact countries move away from one-party rule, the Soviet Union would observe principles of non-intervention and ''absolute freedom of choice.''

Poland, the Soviet Union's largest trade partner, and Hungary have led the way in implementing democratic reform in the East bloc.

But Mazowiecki and his Solidarity-led cabinet have promised to respect the country's military obligations to the Soviet-led alliance.

Government spokeswoman Malgorzata Niezabitowska said last week Poland was preparing a visit by Mazowiecki to Moscow to discuss economic relations, Polish-Soviet history and expanding people-to-people contacts.

Central among the historical issues is the Katyn massacre of 4,300 Polish officers on Soviet soil in World War II.

Speaking to reporters Tuesday, Shevardnadze was asked if they had discussed the issue.

''All questions, everything connected with history - present and future - were raised,'' he replied. ''We are going to study history and search for documents if they exist.

''I state this with full responsibility: We are interested in the truth.''

Poland has been pressing for a joint declaration of Soviet responsibility for the deaths of 15,000 officers at Katyn and two other World War II camps, but there has been reluctance on the part of hard-line factions in the Soviet Union.

Poland also is interested in increasing contact between Soviet citizens and Poles. Staniszewski said Shevardnadze saw no great difficulties in resolving problems of Poles living in the Soviet Union and the care of Polish monuments and places of national remembrance on Soviet territory.