The Russian president, Vladimir Putin, has approved a draft bill for the annexation of Crimea following a referendum in the peninsula that overwhelmingly supported seceding from Ukraine.

In an address to a joint session of Russia’s parliamentary houses scheduled for 11am GMT today, Putin will deliver his position on the hugely contentious Crimean question. His is expected to set the stage for parliament to approve the absorption of Crimea.

The US and the EU retaliated over the referendum – which the west considers illegal – with sanctions against Russian and Ukrainian officials on Monday, a move widely seen as “toothless”.

The White House imposed sanctions against 11 named individuals: seven senior Russian politicians and officials and four Crimea-based separatist leaders accused of undermining the “democratic processes and institutions in Ukraine”.

But the US pointedly avoided targeting Putin or key figures in his inner circle.

The EU imposed sanctions on 21 individuals, including three senior Russian commanders, the prime minister of Crimea, a deputy speaker of the Duma and other senior officials.

There are divisions within Europe over how to respond to Russia, and this is reflected in the fact that action is being taken against fewer than two dozen individuals from an original proposed list of 120.

The sanctions came on the eve of Putin’s address to the Russian parliament. On Monday night, he posted a decree on the Kremlin website recognising Crimea as a sovereign state, in what appeared to be a first step toward integrating Crimea as a part of the Russian Federation. The decree, which took effect immediately, said Moscow's recognition of Crimea as independent was based on “the will of the people of Crimea”.

Putin pressed ahead on Tuesday, informing his government and parliament of the Crimean leadership’s proposal to join Russia ahead of his address to parliament. He was expected to sign the treaty formalising the annexation with Crimea’s leader on Tuesday.

Barack Obama, who is set to visit Europe next week to discuss the crisis with European allies, warned of further action. “If Russia continues to interfere in Ukraine, we stand ready to impose further sanctions,” he said.

Russian troops have also massed near the border with Russian-speaking eastern Ukraine, where there have been fatalities during clashes between pro- and anti-Moscow demonstrators in recent days.

Obama added: “We will continue to make clear to Russia that further provocations will achieve nothing except to further isolate Russia and diminish its place in the world.”

The White House insisted the sanctions were “by far and away the most comprehensive sanctions since the end of the cold war” and rejected criticism that they were too limited in scope or would be easily circumvented by asset transfers.

“We think they will be effective,” one senior administration official told reporters in Washington. But the kind of sanctions that might bite, such as hitting Russian oligarchs or even their companies, particularly energy firms, were pointedly absent.

Officials in Washington suggested that Crimea referendum results showing 96.8% voting in favour of joining Russia and a 83.1% turnout were implausibly high, especially when an estimated 99% of Crimean Tatars refused to take part.

White House sources also claimed it was suspicious that there was not a single complaint to election authorities, and have promised extra funding to help make sure there is a record number of international observers present when Ukraine holds its national elections in May.

The EU condemned the referendum as illegal and said it would not recognise the outcome.

The Crimean parliament, in the aftermath of the referendum, declared independence from Ukraine on Monday and confiscated Ukrainian state property. Crimea also sent a delegation to Moscow to discuss next steps.

Moscow treated the sanctions with derision. The Russian deputy prime minister, Dmitry Rogozin, who faces sanctions on the US list, was dismissive, tweeting that the move drawn up by Obama must have been the work of a “prankster”.

•Excerpted from The Guardian of London. Photo shows President Putin of Russia.