July 28 (Reuters) -

Russia's rouble on Monday fell past the 81 mark to the

dollar for the first time since May 12, reacting to a hefty

interest rate cut last week and U.S. President Donald Trump

shortening his deadline for Moscow to agree a ceasefire with

Kyiv.

Russian stocks also fell as Trump

set a new deadline

of 10 or 12 days for Russia to make progress toward ending

the war in Ukraine or face consequences, underscoring

frustration with Russian President Vladimir Putin.

Friday's 200-basis-point rate cut to 18% was the biggest in

borrowing costs since May 2022, with the central bank hoping to

revive lending and boost flagging economic growth after

stubbornly high inflation showed signs of easing.

The rouble was down 2.1% as of 1513 GMT at 81.0955 per U.S.

dollar, according to data compiled by LSEG based on

over-the-counter quotes.

"It is obvious that the factor of rouble support in the form

of tight monetary policy will gradually start to decrease its

influence on the national currency," Maxim Timoshenko from

Russian Standard Bank, said.

Against the Chinese yuan, the most traded foreign currency

in Russia, the rouble weakened by 2.4% to 11.33.

Russia's benchmark rouble-based MOEX stock index

pared early gains to lose 1.4% on the day, with shares of flag

carrier Aeroflot underperforming the market after a

cyberattack forced the airline to cancel dozens of flights.

Brent crude oil, a global benchmark for Russia's

main export, was up 1.7% at $69.63 a barrel.