ISTANBUL- Turkey secured a tripling of its currency-swap agreement with Qatar to $15 billion, the central bank said on Wednesday, providing much-needed foreign funding to reinforce its depleted reserves and help steady the Turkish lira.

Ankara had been urgently seeking access to funds from Doha and elsewhere to head off a potential currency spiral, and analysts say tens of billions of dollars might be needed. A senior Turkish official told Reuters talks are continuing.

Turkey's central bank said the deal with its Qatari counterpart - which raised the existing FX limit from the equivalent of $5 billion - would support financial stability and trade.

The lira touched a historic low earlier this month as investors fretted over a drop in the central bank's net FX reserves and Turkey's relatively high foreign debt obligations, accelerating Ankara's overseas funding search.

Reuters reported last week that officials from Turkey's Treasury and central bank had appealed to counterparts in Qatar and China about expanding existing swap lines, and to the United Kingdom and Japan about possibly establishing them. 

Turkey has a roughly $1.7 billion swap facility with Beijing.

"Talks on swaps are continuing and especially some are in a very positive situation. We expect positive results from them soon as well," the senior Turkish official said before the central bank's announcement.

The official, who requested anonymity, characterized some of the conversations as ongoing and others as on hold.

The lira has rallied over the last eight trading days on expectations of new funding. Some analysts said the volatility and a 14% drop so far this year risked escalating as in 2018, when Turkey's currency crisis shook emerging markets.

The lira was 0.1% weaker at 6.7900 versus the dollar at 1317 GMT. 

"The extra $10 billion is a drop in the ocean compared to Turkey's external funding needs," especially given hard-hit tourism and trade have widened the current account deficit, said Jason Tuvey, senior economist at Capital Economics.

"We could see pressure on the lira start to mount again" if the Bank of Japan and Bank of England rebuff Turkey, he said.

Net FX reserves at the central bank have fallen to $26 billion from $40 billion this year, in part due to state bank FX interventions to help stabilize the lira, analysts say. Turkey's 12-month foreign debt obligations are $168 billion.

Goldman Sachs analysts said the boost from Qatar "only closes roughly a third of the funding gap we see for 2020."

(Writing by Jonathan Spicer; Editing by Dominic Evans/Mark Heinrich) ((ali.kucukgocmen@thomsonreuters.com , @alikucukgocmen; +902123507067; Reuters Messaging: Reuters Messaging: ali.kucukgocmen.thomsonreuters.com@reuters.net))