HOUSTON, May 1 (Reuters) - The U.S. State Department believes oil services firm SLB has not violated sanctions against Russia and the company has been told what Washington is willing to accept, Assistant Secretary of State Geoffrey Pyatt told Reuters in an interview on Wednesday.

"I have had conversations with the CEO of that company... I think there is a clear understanding within SLB in terms of where the guard rails are on the sanctions policy," Pryatt said.

Since Russia invaded Ukraine, the U.S. and other western countries have sought to reduce Moscow's energy revenue through sanctions that prompted many service companies to leave Russia. SLB has helped Russia keep oil flowing, generating money to fund the war.

"I am confident from my conversations with Treasury colleagues that SLB's actions thus far have been in conformance with rules that OFAC, Treasury and the price cap coalition have set up," Pyatt said.

The U.S. is determined to ensure Russia does not return to being a reliable energy partner and Washington will continue to sanction present and future energy projects, while taking care not to cause oil price shocks, said Pyatt.

SLB was not immediately available for comment. The company had 10,000 employees in Russia helping Gazprom Neft, Rosneft and other top energy firms pump more oil and gas when the war began in 2022 and is the world's largest oil services and equipment provider.

The U.S Treasury is also going after shippers, insurance companies and others that circumvent the sanctions, said Pyatt.

He said Russia's oil and gas tax revenue is down about a third year on year.

Washington is also targeting Russia's future energy projects, including liquefied natural gas (LNG), seeking to prevent Russia from sending the gas that previously flowed to European customers via pipeline to global markets as LNG, said Pyatt.

"So you have seen very strong sanctions against Novatek and there is more to come in the short term on that score," he told Reuters. (Reporting by Curtis Williams in Houston; Editing by David Gregorio)