U.S. Secretary of State George Shultz Wednesday reopened talks on a troubled arms control treaty and said he was sure the Soviet Union wants to resolve differences that led the Senate to shelve the pact indefinitely.

Shultz, before meeting with Soviet Foreign Minister Eduard Shevardnadze, refused to blame the Soviets for differences over how to monitor the destruction of U.S. and Soviet intermediate-range nuclear missiles."I am not trying to characterize the disagreements," he told reporters on his flight from Washington. "Problems have arisen, and since no one has ever done anything like this before, there are problems. We approach this in a problem-solving way."

Soviet Foreign Ministry spokesman Gennady Gerasimov, in a telephone interview Wednesday with the British Broadcasting Corp., said "We think that we can iron out our differences.

"They are not very big," he said, "so we still hope and we think that the Senate is going to ratify the treaty before the Moscow summit." The summit between Reagan and Soviet leader Mikhail S. Gorbachev is scheduled for May 29-June 2.

Shevardnadze, arriving in Geneva on Tuesday, had said he was not sure what the problems over the treaty were. He said the Soviets had answered questions posed by the United States.

"Basically the verification problems regarding the INF (Intermediate-range Nuclear Forces) treaty have been resolved, I think," he said.

In Washington, Sen. Sam Nunn, D-Ga., chairman of the Senate Armed Services Committee, said Wednesday the Senate could ratify the U.S.-Soviet nuclear arms agreement in time for the Moscow summit if Shultz works out disputes in this week's talks.

"I think there's still time to get the consent of the Senate to ratification prior to the summit. But these matters have to be dealt with," he said on ABC-TV's "Good Morning America."

The treaty, signed by Reagan and Gorbachev at the Washington summit meeting in December, is the first to scrap an entire category of nuclear arms. It also provides for unprecedented on-site inspection of missile factories and bases to guard against cheating.

In the past few weeks, the Soviets have raised objections to various procedures proposed by the U.S. side. These include the scope of inspection within designated areas and use of cameras.

Asked if he thought the Soviets were backsliding or causing trouble, Shultz did not criticize Moscow. In fact, he said of Shevardnadze, "He wants to see the INF treaty completed and into operation as much as I do. As problems arise, I am sure he will want to look at them."

Shultz said he hoped the treaty will be ratified before Reagan begins the summit with Gorbachev. But he said, "I can't tell what the Senate will do."

Shultz and Shevardnadze planned to meet twice Wednesday and twice Thursday on the problems and on the wide range of summit topics, including human rights.

The differences over verification have prompted the Senate to postpone indefinitely ratification of the treaty to scrap 683 Soviet missiles and 364 U.S. rockets.

With the Moscow summit less than three weeks away, the trouble over the treaty is a severe setback to the arms control process.

Already, there is virtually no hope of completing a second accord to sharply reduce long-range U.S. and Soviet nuclear weapons before the summit.