Qatar's ambassador to Russia, Fahad bin Mohamed Al-Attiyah, said QIA's stake opened the door to cooperation between Rosneft and Qatar Petroleum in projects around the world.
"There is no 'malicious agenda'," Al-Attiyah said. "Just pure economic reasons."
Qatar is seeking international partnerships amid a boycott imposed by Saudi Arabia, the United Arab Emirates, Bahrain and Egypt, which severed diplomatic and transport ties with the country in 2017, accusing it of supporting terrorism. Doha denies the charge.
Qatar's joint projects with other energy firms do not raise eyebrows, he said. "So then why is there a question mark when we have a collaboration with Rosneft"
Reuters reported last year that Russian state bank VTB secretly loaned around $6 billion to QIA to help finance its acquisition of the Rosneft stake, undermining the deal's stated aim of bringing foreign money into Russia.
Rosneft denied the report.
Al-Attiyah said he did not know whether Russian funds were used to finance the deal. Qatar could sell the stake but was unlikely to do so soon, he said.
"We did not invest that much of a stake into this company to flip just like this, very quickly," Al-Attiyah said.
GAS, AIR DEFENCE
The United States has called on Qatar, one of the world's top suppliers of liquefied natural gas (LNG), to challenge Russian gas dominance in Europe.
But the tiny Gulf nation will not be at loggerheads with Russia over the European market on political grounds, Al-Attiyah said.
"We are ... in the space of the same commodity and we do want to expand our markets," he said. "If that expansion comes within the natural course of economic partnership, then absolutely fine."
"But if it comes within the context of any political rivalry, then absolutely we will say no to that ... Why try to push somebody out"
Qatar could also partner in Russian LNG projects, though participation in Novatek's NVTK.MM Arctic LNG 2 has not come up in discussions, he said.
Al-Attiyah confirmed that Qatar was in talks about buying Russian air defence systems, but said no contracts had been signed due to sanctions on Russian military exports.
The sanctions "created considerable concern", Al-Attiyah said.
Saudi Arabia previously threatened to take military action if Qatar installed the Russian S-400 air defence system.
"We don't tell the Saudis what they should buy," Al-Attiyah said. "And we won't let them interfere in our relationships with Russia."
(Writing by Polina Ivanova; Editing by Dale Hudson) ((firstname.lastname@example.org;))