MOSCOW - The Kremlin on Thursday explained President Vladimir V. Putin's surprising decision to skip a planned high-profile visit to the United States next week by saying he needs to finish setting up his new government. Although this may sound like a lame excuse, it could actually be true. Or not.

Theories abound on why Putin decided not to join global leaders for a meeting outside Washington and to postpone a much-anticipated meeting with President Obama.

Some suggest Putin wanted to avoid Western criticism over the police crackdown on protesters that began in earnest on the eve of his return to the presidency Monday. Others speculate that the social tensions themselves are what is keeping him close to home.

But Putin's job swap with Dmitry A. Medvedev, the former president who is now prime minister, has created tensions of its own within Russia's ruling elite. Who will serve in the cabinet under Medvedev and what role will be played by other top Putin allies who object to being subordinate to Medvedev? No appointments have yet been made.

The White House announced Wednesday that Medvedev would represent Russia at the summit meeting of the Group of Eight industrial nations at Camp David next Friday and Saturday. Obama's first meeting with Putin as Russia's president is now due to take place at another global summit, in Mexico on June 18-19.

The younger and seemingly more Western-leaning Medvedev has been Obama's partner in the U.S. effort to "reset" the two countries' strained relations, while Putin, whose outlook was formed during the Cold War, has been more suspicious of U.S. intentions.

During the months before the March presidential election, Putin made criticism of the United States a central theme of his campaign. But now that he is back in the Kremlin he is expected to take a more pragmatic approach to relations with the West, especially in light of Russia's dire need for foreign investment.

Putin's return to the presidency has been soured by a series of protests that have been broken up by police, with hundreds of people detained. At least 20,000 people turned out for an opposition rally on the eve of his inauguration, far more than expected as the protest movement had appeared to be fizzling.

On Monday, as Putin was sworn in for a third term in a regal Kremlin ceremony, helmeted riot police chased demonstrators through the streets of Moscow to prevent them from protesting. Throughout the week, hundreds of protesters have continued to play a game of cat-and-mouse with police.

Some see Putin's cancellation of the Washington trip as an effort to avoid uncomfortable questions about the crackdown on dissent.

Putin, however, has often relished an opportunity to take on his critics both at home and abroad.

At a summit with European Union leaders in Brussels, Belgium, in 2002, where he was criticized over the military campaign against Islamic extremists in Chechnya, he famously struck back by telling those who supported the extremists that he could arrange for them to be circumcised in such a way that "nothing will grow again."