(Adds analyst comment, Halkbank, bonds)
By Behiye Selin Taner
ISTANBUL, Nov 14 (Reuters) - The Turkish lira weakened on Thursday after U.S. President Donald Trump pushed President Tayyip Erdogan to walk away from the purchase of a Russian missile defence system, calling it a "very serious challenge" to bilateral ties.
The lira stood at 5.7620 against the dollar at 0635 GMT, weakening some 0.3% from Wednesday's close of 5.7450. The Turkish currency has weakened around 8% this year, mainly on concerns over deteriorating U.S. ties.
Trump described a meeting between the two leaders as "wonderful" but both leaders fell short of explaining in concrete terms how they would overcome the mounting differences they have on numerous issues.
"There is a neutral outcome from the markets' perspective," said Ata Invest director Cem Tozge, saying there were no clear messages on key issues between the two countries. "The market will continue in a monitoring mode after this," he added.
The United States and Turkey have been at odds over Syria policy, Turkey's purchase of Russian S-400 missile defences, the trials of U.S. local consulate workers in Ankara and the case against Turkey's Halkbank in a New York court.
"The Halkbank subject did not come onto the agenda at the news conference. It could have been discussed behind the scenes of course," Tozge said.
Shares in Halkbank fell 3% at the opening and were down 1.85% at 0715 GMT. The main share index was up 0.28%.
The lira came under pressure earlier this year as Ankara faced U.S. sanctions due to its purchase of the Russian S-400s. It also weakened in October when Turkey launched an operation in northeast Syria against the Kurdish YPG militia, a U.S. partner, again raising the prospect of sanctions.
While investors await details on what happened behind closed doors in the talks, they are also starting to turn their attention to the next Turkish Central Bank policy-setting meeting on Dec. 12, where a further rate cut is expected.
The central bank slashed its policy rate to 14% last month, taking advantage of an inflation dip. The bank's governor subsequently said the room for further cuts was dwindling.
The benchmark 10-year bond yield was at 12.59% at Wednesday's close and at 12.47% in the last value-dated trade. In May the bond yield stood at 21%. (Writing by Daren Butler; Editing by Dominic Evans)