UPDATE 1-Delhaize ups Alfa-Beta offer to 34 euros/share

* Delhaize ups Alfa-Beta offer price 11.5 pct to 34 euros

* Says two major shareholders agreed to sell at new price

* Delhaize says has 65.86 pct of Alfa-Beta vs 65.27 before

* Alfa-Beta up 11.3 pct to 34 euros, Delhaize down 1 pct

* Offer ends Thursday, July 9

(Updates with additional background, analyst, detail)

BRUSSELS, June 29 (Reuters) - Supermarket group Delhaize (DELB.BR) said it was raising its offer price for partially-owned Greek unit Alfa-Beta Vassilopoulos ABVr.AT to 34.00 euros ($47.60) a share, with key investors backing the deal.

The announcement on Monday immediately sent Alfa-Beta's shares up 11.3 percent to 34 euros, matching the new offer.

Belgium's Delhaize, which became Alfa-Beta's principal shareholder in 1992, said the Vassilopoulos family, which holds 7 percent of the remaining Alfa-Beta shares, had agreed to sell at the new price which is 11.5 higher than before.

The new offer values the whole of Alfa-Beta at 433 million euros, compared with 388 million euros under the previous offer, KBC Securities analyst Pascale Weber said.

It said another unnamed shareholder, which holds about 5 percent of the shares, had also signed up to the new price.

With these heavy-weight investors now locked into selling, Delhaize hopes to pressure smaller shareholders to sell as well, a source close to the matter said.

With the offer closing on July 9, Delhaize had so far scooped up precious few Alfa-Beta shares with the previous price of 30.50 euros a share.

Delhaize said it now held 65.86 percent of Alfa-Beta, versus the 65.27 percent it held before the start of the tender offer.

In its statement, Delhaize said its Delhaize "The Lion" Nederland subsidiary, making the Alfa-Beta buy, did not intend to increase the tender offer price further.

Delhaize generates about 70 percent of its sales in the United States where it operates a variety of supermarket chains, including Food Lion.

It also has supermarkets in Greece, Romania and Indonesia.

Delhaize shares traded down 1 percent at 49.30 euros as of 0804 GMT. ($1=.7143 Euro) (Reporting by Anne Jolis in Brussels, additional reporting by Harro ten Wolde in Amsterdam)