* Lira firms after falling for five sessions
* Global outlook stays rosy as U.S.-China deal nears
* Russian stocks hover near record highs
* Philippine peso underperforms
By Sagarika Jaisinghani and Aaron Saldanha
Dec 20 (Reuters) - Emerging market assets were mostly flat on Friday as trading thinned ahead of the Christmas holidays, while the Turkish lira firmed after falling for five straight sessions in the wake of worsening political ties between Ankara and Washington.
The lira rose 0.4% and was on course for its best day in a month. The currency, still nursing losses after sliding nearly 30% last year, has come under pressure as the United States steps up efforts to punish Turkey, partly for its purchase of Russian S-400 defence systems.
The lira also missed out on a broader trade-fuelled rally this week, which put the MSCI index of emerging market currencies on track for three straight weeks of gains.
Investors, comforted by a preliminary trade truce between the United States and China, are viewing riskier assets in the developing world more favourably towards the end of the year.
U.S. Treasury Secretary Steven Mnuchin said on Thursday the world's top two economies would sign their "phase one" trade pact in early January, adding that it had already been put down on paper and would not be subject to renegotiation.
"Going forward, 'phase one' implies a 'phase two' so markets will be keeping a close eye on what this actually means in the broader scheme of things and whether a further de-escalation in tariffs is going to commence," said Simon Harvey, FX analyst at Monex Europe.
After underperforming the S&P 500 for most of 2019, a basket of emerging market stocks is on course in December for its best month since January, also powered by easing recession fears and a slightly rosier view on Brexit.
But in the absence of major updates on the trade war and fresh economic data, analysts said stocks had little motivation to change from current levels. Trading is also winding down in the run-up to the holidays.
Russian stocks stayed near all-time highs on Friday, boosted by the country's largest gas producer Gazprom .
Analysts said an agreement between Russia and Ukraine about gas supplies opens the door for Gazprom's shares to advance to 260 roubles per piece compared with their current price of around 253.
Turkish equities added about 0.9%, while South African shares were nearly flat. Chinese shares ended the day lower, but were still up about 1.2% on the week.
Among currencies in the developing world, South Africa's rand and Russia's rouble firmed slightly against the dollar. The Philippine peso underperformed regional peers, weakening 0.4% in its worst session in over a month.
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For RUSSIAN market report, see (Reporting by Sagarika Jaisinghani and Aaron Saldanha in Bengaluru; Editing by Susan Fenton)