China National Petroleum Corp., or CNPC, owes Russian companies $180 million for unpaid oil bills in the first three months of the year, Russia 's oil pipeline operator OAO Transneft (TRNFP.RS) said Thursday.

Under a loan-for-oil deal the two countries signed last year, Russian oil producer OAO Rosneft (ROSN.RS) started supplying crude to
China via a new cross-border pipeline on Jan. 1.

From January to March, CNPC has paid $38 million less a month than agreed to Rosneft and $22 million less monthly to Transneft, a Transneft spokesman said. Chinese foreign ministry spokesman Hong Lei said earlier Thursday that the dispute could be resolved "through friendly consultations."

Rosneft declined to comment.

Under the deal signed last year,
China provided Rosneft and Transneft with $25 billion in long-term capital. In exchange, Russia agreed to export 15 million metric tons of crude to China in each of the next 20 years starting this year.

Talks were planned to take place in May, but so far no meetings have been agreed, Transneft said.

"If there aren't any negotiations in May, we will have to take the Chinese to court," the Transneft spokesman said.

Russian oil supplies started on Jan 1 through a new 1,000-kilometer pipeline extending from the eastern Russian town of
Skovorodino , close to the Chinese border, to the oil production and refining hub of Daqing in northeast China .

The dispute has not affected the contracted supplies, Transneft said.