By Jonny Dymond BBC correspondent in Istanbul

The Turkish parliament has passed amendments to the country's constitution that would allow the leader of the governing party, Recep Tayyip Erdogan, to sit in parliament.

The amendments have already been vetoed once by the Turkish President, Ahmet Necdet Sezer.

Mr Erdogan was barred from parliament because of a conviction for inciting religious hatred.

The ball is back in the president's court.

PRESIDENT'S OPTIONS

Accept the unchanged amendments Refer them to the constitutional court Call a referendum on the changes

President Sezer vetoed the amendments last week because they were, he said, subjective and personal - that is to say they were aimed entirely at getting Mr Erdogan into parliament.

The constitution bars from parliament those who have been convicted of what are called ideological crimes - in Mr Erdogan's case, a conviction for inciting religious hatred by quoting a well-known poem in a speech he made.

When his party came to power in late November, it set about changing the constitution so that Mr Erdogan could stand.

In this, it has had the opposition's support.

Rare by-election

Now President Sezer has a choice: he can accept the unchanged amendments, refer them to the constitutional court or call a referendum on the changes.

A referral or a referendum would delay the reforms, and delay could scupper Mr Erdogan's chances of getting into parliament swiftly.

A by-election - something of a rarity under the Turkish political system - is scheduled for early February.

If the constitution is not changed by late January, Mr Erdogan will be unable to stand.