The United States is voicing concerns about Russian fuel shipments to North Korea. The United Nations has capped the amount of refined petroleum products that can be sent to North Korea as part of its long effort to curb that country’s nuclear weapons program. But the White House says Russia is shipping fuel to the communist North at levels that exceed U-N Security Council limits. Officials here say intelligence shows that Russia has become increasingly reliant on North Korea for arms for its war in Ukraine — and the administration is prepared to impose new sanctions.