LONDON — For major oil companies these days, geopolitical acumen is as essential as deepwater engineering. Just ask the British oil giant BP.

The company’s ambitions in Russia were dealt another setback Friday when an arbitration tribunal upheld an injunction that indefinitely blocks its share-swap agreement with the state-owned oil company Rosneft.

BP’s chief executive, Robert Dudley, might still be able to salvage the approximately $7.8 billion Rosneft deal. But Friday’s ruling may indicate how seriously Dudley misread Russian politics in striking that agreement — or was overtaken by developments that even the most expert Kremlinologist might not have been able to anticipate.

Either way, the ruling puts new pressure on BP to appease its partners in a separate and private joint venture in Russia, a group of billionaires who opposed the Rosneft deal. That group won the injunction two weeks ago from an arbitration tribunal in Sweden, arguing that the deal with the state-owned oil giant had breached their own shareholder agreement with BP in their partnership, called TNK-BP.

BP in a statement Friday said the ruling was simply a deferral and that the company would continue with arbitration hoping for a favorable final ruling. But the statement also said, “We will now also be exploring possibilities for a reasonable commercial solution with all parties.”

The Russian billionaires in TNK-BP, who do business as a group known as AAR, issued a statement Friday calling the tribunal’s ruling “fair, balanced and thoughtful.”

“We will be pleased to continue to cooperate with the tribunal and will provide any additional information and evidence it requires during the next stage of the hearings,” Stan Polovets, AAR’s chief executive, said in the statement.

Prospects looked decidedly better for BP in mid-January, when Prime Minister Vladimir Putin of Russia presided over the signing ceremony for the Rosneft agreement. The deal called for the companies to invest in each other through a stock swap representing about 5 percent of BP and 9.8 percent of Rosneft, and to also jointly explore new oil fields in the Russian Arctic.

It seemed a strategic victory for Dudley, the American who rose to the top post at BP after the Deepwater Horizon spill in the Gulf of Mexico last year.

On taking that job in October, he quickly sold more than $22 billion of BP assets to help pay claims and cleanup costs and to focus on the company’s most lucrative operations. Then came the deal with Rosneft, which looked to be Dudley’s first bold move to help the company expand in new directions.

But now, with the suspended Rosneft deal having cost the company more time and investor support than planned, Dudley will probably find himself facing hard questions when BP holds its annual shareholder meeting in London on Thursday.

A bad bet

One of the hardest things to explain might be how he could have stumbled in Russia, after having spent five years in Moscow running the TNK-BP joint venture from 2003 to 2008. Or why he had not anticipated the tough tactics the TNK-BP partners might employ. After all, Dudley’s previous Russian experience led to his being forced into hiding in 2008 after disputes with the government and those same partners led to the revocation of his work visa.

This time, it had appeared that Dudley and BP might have protection from higher-ups. Rosneft’s chairman, Igor Sechin, is also a powerful deputy prime minister.

It turned out to be a bad bet on BP’s part. Even at the Jan. 14 signing ceremony, according to one person who was present, Putin had mentioned in a quiet aside that the AAR group was known to be litigious. What had seemed a passing remark proved to be predictive.

The AAR billionaires began threatening to sue almost immediately.

“BP assumed that any difficulties with the local shareholders would be resolved at a local level,” Christopher Weafer, the chief analyst at Uralsib bank, said in an interview. “That hasn’t happened. At least it hasn’t happened yet. It has to happen now.”

Oil analysts, too, say that Sechin, BP’s patron, may not have been as powerful as the company had hoped — or that if he was sufficiently powerful in January, he no longer is.

Dmitri Medvedev, the president of Russia, recently ordered ministers to step down from the boards of state-controlled companies, citing conflicts of interest. The change will deprive Sechin of his position at Rosneft, unless he resigns as deputy prime minister instead.

Putin, too, now seems to be distancing himself from the BP-Rosneft deal. In March, he told Russian journalists at a news conference that Dudley had not warned him of the possible legal challenge from the Russian oligarchs.

The AAR partners have denied using the legal challenge to try to negotiate a sale of their shares.

Gaining access

Some investors would welcome the Rosneft deal despite its problems, according to Keith Bowman, an analyst at the brokerage firm Hargreaves Lansdown. From that viewpoint, any link with Rosneft would make it easier for BP to win future exploration contracts in Russia, the world’s largest oil-producing country.

And yet, despite Dudley’s tempestuous history with the TNK-BP partners, that venture has been a financial success for BP to date. Through it, BP’s operations in Russia have become as important to the company as those in the United States. After contributing about $6 billion in cash and assets to the founding of the TNK-BP venture in 2003, BP has since then made $14.3 billion in dividends from it — it still retains 50 percent of the assets.

And so even as BP fights with the oligarchs over the Rosneft deal, the TNK-BP joint venture is itself an important part of the British company’s portfolio.

“Any natural resources company’s biggest aim is to access new resources,” said Philip Weiss, an analyst with Argus Research in New York. “It’s a bit more important for BP because of the questions hanging over them in the Gulf.”