Greek letter: Are the concessions enough?

European markets rose on Wednesday after a letter from Greek Prime Minister Alexis Tsipras to creditors boosted hopes of a deal on reforms, but analysts warned that investors could be getting ahead of themselves.

Tsipras sent the letter on Tuesday as part of a request for further financial aid, although it only became public on Wednesday.

The Greek leader appeared to offer some concessions on reform plans, but also stuck to his guns on other proposals, such as maintaining a 30 percent discount on the VAT (sales tax) applied to Greek islands which lenders want abolished.

Read MoreTsipras letter suggests Greece climbdown

European equities rallied 2 percent on the news, first reported by Financial Times, but analysts were divided on whether the concessions would be enough for a deal with creditors.

Peter Chatwell, an interest rate strategist at Mizuho International, said the letter was "not the climbdown that it seems."

"I strongly doubt Europe will accept this proposal and if Europe sticks to its guns and waits for the referendum, the greater the chance that the government fails," he said in a note.

While Carsten Brezski, senior economist at ING, told CNBC the letter was "another tactical move to stay ahead of the euro zone in the ongoing blame game, rather than a serious change of mind."

"In my view, the euro zone will not move any more ahead of the referendum," he added.

Demonstration in Syntagma square in support of a YES vote in the 5th of July Referandum in Greece on July 30 2015.
George Panagakis| Pacific Press | LightRocket via Getty Images
Demonstration in Syntagma square in support of a YES vote in the 5th of July Referandum in Greece on July 30 2015.

However, Craig Erlam, senior market analyst at forex trading platform OANDA, argued that the letter marked "an incredible U-turn from the Greek Prime Minister."

"Of course, the acceptance (of creditors' demands) does come with conditions attached which is hardly surprising, but they do appear to be watered down compared to previous demands," he said, adding that lenders might be willing to consider the proposals.

Read More'The mood is black': Greeks struggle amid crisis

Greece is currently stranded in financial no-man's land, without a bailout program -- which expired at midnight last night -- and heading towards a referendum on whether to accept more austerity. If Greeks vote "no" to the reform proposals on Sunday, the county could leave the euro zone.

The Eurogroup will hold a conference call on Greece at 4.30 p.m London time on Wednesday to discuss the situation.

Third bailout coming?

Also crucial for Greece, whose banking system has been paralyzed by capital controls imposed to prevent mass deposit withdrawals, is a meeting of the European Central Bank (ECB) on Wednesday. The bank is expected to review its emergency liquidity assistance (ELA) for Greek lenders, which it capped this weekend.

The ECB is also likely to take into consideration the fact that Greece effectively defaulted on a large debt due to the IMF on Tuesday, and has a payment due to the ECB in July.

Read MoreGreece crisis: Athens asks for new bailout, Merkel hits the brakes

The IMF confirmed on Tuesday that Greece did not make the 1.5 billion euro ($1.7 billion) debt repayment and was now "in arrears." Spokesman Gerry Rice said Greece would only receive further IMF funding when the arrears were cleared.

The missed payment was widely expected following the collapse of talks at the weekend between Greece and its international lenders on reforms. Had the negotiations succeeded, Greece could have received a last tranche of bailout aid with which to pay its debts

'No future outside EU'

Rather than capitulate to lenders after five months of fraught talks, Tsipras at the weekend made the surprise move of calling a snap referendum on Greece's bailout program and austerity measures. Ahead of the vote on July 5, both anti-austerity and pro-European protests have been taking place in central Athens, with tens of thousands of people in attendance, according to media reports.

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A poll by published in the broadly pro-government newspaper Efimerida ton Syntatkton on Wednesday found that 54 percent of Greeks would vote "no" to the bailout proposals, but the lead was narrowing.

However, Anna Diamantopoulou, president of Greek think-tank To Diktyo, told CNBC Tuesday that the "yes" vote – which would mean accepting austerity measures, such as pension and wage cuts, and remaining in the euro zone -- would "win at the end of the day."

"This is because Greek people, even in this difficult situation, are still very much pro-European and they do believe that Greece has to be part of the European Union," Diamantopoulou, who is the former education minister for Greece's PASOK party, said. "There is no life for Greece outside the European Union."

-CNBC's Julia Chatterley contributed reporting to this story by Holly Ellyatt, follow her on Twitter @HollyEllyatt. Follow us on Twitter: @CNBCWorld