Britain is under increasing direct and indirect pressure to stay within the European Union.

Prime Minister David Cameron received a call from U.S. President Barack Obama urging him not to consider withdrawing from the EU, news media reported. White House aides confirmed the president had telephoned Cameron.

Obama made the call just before Cameron was to make a speech in the Netherlands Thursday that could have outlined his plans for the EU. Cameron canceled the speech as the Algeria hostage crisis unfolded.

In the speech Cameron planned to warn the British people would "drift towards the exit" from the European Union unless the EU is reformed, The Independent said.

"There is a gap between the EU and its citizens which has grown dramatically in recent years and which represents a lack of democratic accountability and consent that is -- yes -- felt particularly acutely in Britain," Cameron's draft said.

"If we don't address these challenges, the danger is that Europe will fail and the British people will drift towards the exit."

"I do not want that to happen. I want the European Union to be a success and I want a relationship between Britain and the EU that keeps us in it."

The speech was due to be delivered at a meeting in Amsterdam.

A White House spokesman said while Cameron "set forth his thinking on U.K.-EU relations in light of his upcoming speech," Obama "underscored our close alliance with the United Kingdom and said that the United States values a strong U.K. in a strong European Union."

The Independent called the often postponed speech a disaster.

"He intended to deliver it in the autumn; then before Christmas," Andrew Grice of The Independent wrote.

"Then it was fixed for next Tuesday, a diplomatic disaster as it clashed with the 50th anniversary of the Franco-German reconciliation treaty after the Second World War. That the British government didn't know there was a big love-in in Berlin shows how we have drifted to the EU's margins, if not quite the exit door."

Cameron is under increasing pressure not only from pro-European business and opposition political parties but also from rival factions inside his Conservative Party. He wants to renegotiate terms under which Britain would stay within the EU.

A group of 25 pro-EU Conservative lawmakers wrote to the prime minister urging him to set out a "positive British vision for leadership in Europe."

"We are concerned that an over-emphasis in your speech on renegotiation and a referendum rather than leadership could undermine the [EU] single market. The U.K. has potential allies on many key issues, even on the merits of repatriating some powers."

The lawmakers include former Cabinet ministers Malcolm Rifkind, Caroline Spelman and Stephen Dorrell, the BBC said.

"We fear that a renegotiation which seems to favor the U.K. alone would force other capitals to ask why they cannot simply dispense with those parts of the single market that don't suit them," the lawmakers said in their letter to Cameron.

Opposition to an EU exit has come not only from "back bench" Conservative lawmakers who don't hold government posts but also from a senior Conservative, former Deputy Prime Minister Michael Heseltine, a government adviser on economic growth.

In interviews with the Times and the Financial Times, Heseltine criticized Cameron's European strategy and warned an "ill-advised" referendum on EU member would jeopardize British business and drive away inward investment.

The Confederation of Business Industry, a leading business lobbying group, warned Cameron to "treat carefully" on Europe.

CBI Director General John Cridland said, "We need to recognize and adapt to the realities of the multi-speed Europe which is emerging."

He said, "The fallout in the eurozone from the debt crisis is not just forcing through rapid political and financial integration. It is also forcing all countries to fundamentally rethink the EU's wider purpose and deal urgently with the sort of structural flaws Europe has ignored for decades.

"We must tread very carefully though. The debate about our future in Europe in 2013 must be based on an informed, hard-headed analysis of where our long-term economic and financial interests lie and business will need to make its voice heard."

"We need global trade deals to drive growth and create jobs, especially when the domestic economy is growing more slowly than required. Businesses don't want the baby thrown out with the bathwater -- not with 50 percent of our exports heading to Europe."