Iranians investigating the downing of a passenger plane a year ago are deliberately dragging their feet, according Ukraine International Airlines.
Tehran has said its anti-air missiles brought down the plane by mistake on January 8 last year, killing all 176 passengers and crew during a period of heightened tension with the US.
"We haven't got an answer to the main question: how could this happen and who is responsible?" UIA chief Yevhenii Dykhne said. "The process isn't moving".
"The tactic on the Iranian side is to sweep under the rug, to drag their feet," he said. "There needs to be more serious pressure from those countries whose citizens died."
Ukrainian officials confirmed this week they received a preliminary "technical report" from Iran on December 31 on the circumstances of the disaster.
They now have two months to review the document and decide if they are satisfied.
Mr Dykhne joined widespread criticism of Tehran's offer to give $150,000 to the families of each of the victims as a "media strategy just designed to test our reaction".
He said the Iranian government has not made any official proposal for payouts, arguing that "international precedents" should be used to set the level of compensation.
Payouts should only follow technical and criminal inquiries into the deaths and a determination whether the destruction of the plane was due to human error or a planned "military" act, Mr Dykhne said.
Canadian Prime Minister Justin Trudeau last month called on Iran to answer questions about the plane, in which 55 Canadians were killed. An independent report complained that Iran was "investigating itself, largely in secret".
The report said Iran's probe suffered "obvious conflicts of interest... with few safeguards to ensure independence, impartiality or legitimacy".
In 1996, Washington agreed to pay a total of $61.8 million to the families of 290 people killed in an Iran Air plane shot down by a US warship in 1988.
After its 2003 admission of responsibility for the 1988 Lockerbie bombing of a US-bound passenger plane, Libya paid $2.7 billion to the families of the 270 people killed.
