WASHINGTON — The Trump administration opened the door to a potential White House meeting between President Donald Trump and Russian President Vladimir Putin on Monday, raising the possibility of an Oval Office welcome for Putin for the first time in more than a decade even as relations between the two powers have deteriorated.

The Kremlin said Monday that Trump had invited the Russian leader to the White House when they spoke by telephone last month. White House press secretary Sarah Huckabee Sanders responded that the White House was among “a number of potential venues” discussed. Both sides said they hadn’t started preparations for such a visit.

If it happens, Putin would be getting the honor of an Oval Office tete-a-tete for the first time since he met President George W. Bush at the White House in 2005. Alarms rang in diplomatic and foreign policy circles over the prospect that Trump might offer Putin that venue without confronting him about Russia’s interference in the 2016 presidential election or allegations that Russia masterminded the March 4 nerve agent attack on a former Russian double agent.

“It would confer a certain normalization of relations and we’re certainly not in a normal space,” said Alina Polyakova, a foreign policy fellow at the Brookings Institution. “Nothing about this is normal.”

Much has happened since Trump and Putin spoke in the March 20 phone call. Trump said afterward he hoped to meet with Putin “in the not too distant future” to discuss the nuclear arms race and other matters. But their call was followed by reports that Trump had been warned in briefing materials not to congratulate the Russian president on his re-election but did so anyway.

Since the call, two dozen countries, including the U.S. and many European Union nations, and NATO expelled more than 150 Russian diplomats in solidarity with Britain over the poisoning of Sergei Skripal, the former spy, and his daughter Yulia. Moscow has denied any involvement in the nerve attack and retaliated by expelling the same number of diplomats from each nation.

Putin’s foreign affairs adviser, Yuri Ushakov, told reporters Monday that when the two leaders spoke by phone, “Trump suggested to have the first meeting in Washington, in the White House,” calling it a “quite interesting and positive idea.”

Ushakov voiced hope that tensions resulting from the diplomatic expulsions wouldn’t derail discussions about a summit.

Trump has said maintaining a strong personal relationship with Putin is in the U.S. interest and has signaled to allies that he trusts his own instincts in dealing with the Russian president.

A White House official, speaking on condition of anonymity to describe private discussions, said Trump raised the possibility of a White House meeting in a “casual, open-ended” fashion during the call. The official reiterated that no extensive preparations had taken place.

Talk of a White House summit comes as Trump is preparing to meet North Korean leader Kim Jong Un at an undetermined location. White House welcomes are typically reserved for friends and allies.

Trump has avoided criticizing Putin personally even as his administration has crossed Moscow by providing Ukraine with lethal weapons and upholding Obama-era sanctions against Russia and its shuttering of diplomatic outposts.

Michael McFaul, who served as the U.S. ambassador to Russia under President Barack Obama, said the “symbolism of Putin standing in the East Room with the president at a news conference” would be a major goal for the Russian leader. “The only reason you should do it is if you’re going to obtain a concrete objective that serves America’s national security interest before the meeting,” he said.

McFaul said he feared that Trump “thinks that a good meeting with Putin is the objective of his foreign policy with Russia. That should never be the objective. That should be the means to achieve things that are actually of importance to the United States.”

Trump had already fallen under sharp criticism from some Republican lawmakers for congratulating Putin on his re-election during the call and for not raising the ex-spy’s poisoning. The fact that Trump also extended a White House invitation during that call was likely to increase concerns that Trump, when in direct contact with Putin, is inclined to offer olive branches and reluctant to raise difficult issues.

“I worry that Trump wittingly or unwittingly may be sending a more positive signal to Putin than he deserves,” said Nicholas Burns, a top State Department official during the Bush administration who also served as U.S. ambassador to NATO.

Russia’s disclosure of the invitation came the day before the leaders of three Baltic countries — Latvia, Lithuania and Estonia — were to visit the White House. The three NATO nations are seen as a bulwark against Russia’s aspirations of extended influence west of its border.

Trump has met Putin twice as president, at the Group of 20 summit in Germany last summer and briefly at the Asia-Pacific economic summit in Vietnam in November.

Putin, who was president of Russia once before, visited the White House in 2005, when Bush welcomed him in the East Room as “my friend.”

Putin has been to other parts of the U.S. frequently in recent years, including a visit to the Bush family compound in Maine. Putin’s meetings with Obama occurred at international summits and along the sidelines of the United Nations gathering in New York.

Obama met Russian President Dmitry Medvedev at the White House in 2010, when the pair also chowed down on burgers at a popular hamburger joint outside the capital.

Associated Press writers Vladimir Isachenkov in Moscow and Josh Lederman in Washington contributed to this report.