The U.S. has been helping Ukraine mount long-range strikes on Russian energy facilities for months in a joint effort to weaken the economy and force President Vladimir Putin to the negotiating table, the Financial Times reported on Sunday.

U.S. intelligence has helped Kyiv strike important Russian energy assets, including oil refineries, far beyond the front line, the newspaper said, citing unnamed Ukrainian and U.S. officials familiar with the campaign.

The White House, Ukrainian President Volodymyr Zelenskyy's office and Ukraine's foreign ministry did not immediately respond to Reuters requests for comment. There was no immediate comment from the Russian foreign ministry.

Moscow said this month that Washington and its NATO alliance were regularly supplying intelligence to Kyiv in the war Putin launched in February 2022.

"The supply and use of the entire infrastructure of NATO and the United States to collect and transfer intelligence to Ukrainians is obvious," Kremlin spokesman Dmitry Peskov told reporters then.

The FT said U.S. intelligence helps Kyiv shape route planning, altitude, timing and mission decisions, enabling Ukraine's long-range, one-way attack drones to evade Russian air defenses.

The United States is closely involved in all stages of planning, it said, citing three people familiar with the operation. A U.S. official was quoted as saying Ukraine selected the targets for long-range strikes and Washington then provided intelligence on the sites' vulnerabilities.

Early this month two U.S. officials told Reuters that Washington would provide Ukraine with intelligence on long-range energy infrastructure targets in Russia, as it weighs whether to send Kyiv missiles that could be used in such strikes.

The U.S. also asked NATO allies to provide similar support, the U.S. officials said.

Zelenskyy said on Saturday he had discussed Russian attacks on the Ukrainian energy system in a "positive and productive" call with U.S. President Donald Trump.

"We discussed opportunities to bolster our air defense, as well as concrete agreements that we are working on to ensure this. There are good options and solid ideas on how to truly strengthen us," Zelenskyy posted on X.