U.S. officials said the United States and the Soviet Union are very close to final agreement on a historic treaty limiting strategic nuclear weapons, but after some recent disappointments nobody is flatly predicting a final breakthrough in this week's talks in Houston.

The strategic reduction arms talks - or START - would cut the total number of nuclear warheads and missiles by an overall total of about 35 percent, including a 50 percent cut in the largest and most accurate of Soviet missiles.A senior administration official, speaking on the basis of no further identification, said that the treaty could be put away at the talks Monday and Tuesday in Houston between Secretary of State James Baker and Soviet Foreign Minister Eduard Shevardnadze.

But the official said, "The deadline is not as important as the quality of the eventual treaty and there is an immense amount of sheer volume, 500 pages of highly technical documents with every word having to be checked and translated."

The biggest remaining problem, said the official, is the specifics of verifying the limits. There are about a dozen different inspection and verification techniques, including surprise on-site visits to missile sites and production facilities.

The verification is far more complex than the Intermediate Nuclear Forces treaty signed three years ago at the Ronald Reagan-Mikhail Gorbachev summit in Washington. In INF, a whole class of missiles was eliminated so the confirmed existence of a single missile of that class would be a clear violation of the treaty.

In START, only a proportion of each type of weapon would be eliminated. So, in order to confirm a violation, every weapon of that class has to be located and counted to see if one side has too many.

But the INF treaty set an important precedent - the Soviets giving in to the principle of intrusive on-site inspections by U.S. inspectors.